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• Do busy smtp servers use long running tcp connections to exchange lot of mails?

  - by iamrohitbanga

  I had this idea from http://stackoverflow.com/questions/2813326/maximum-number-of-bytes-that-can-be-sent-on-a-tcp-connection is it possible that smtp servers like gmail and yahoo enter into some form of agreement to maintain a tcp connection between them so that lots of mails could be sent on the same tcp connection. it would be efficient as there would be heavy mail traffic between these mail servers.

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• TCP Flow control in AS3?

  - by Jeremy Stanley

  I am currently working on a Flash socket client for a pre-existing service/standard. The service uses TCP flow control to throttle itself and the Flash socket is reading in everything as fast as it can despite not being able to process it as fast as it's being taken in. This causes the bytesAvailable on the socket to keep increasing and the server never knows that the client has fallen behind. In short, is there any way to limit the size of bytesAvailable for a Flash Socket object or throttle it in some other way? Note: Rewriting the server isn't a viable option at the current time as it's a standard and the client's utility drops immensely if server-side changes are needed

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• questions about multi threading for sockets/tcp-connections.

  - by Fantastic Fourier

  I have a server that connects to multiple clients using TCP/IP connections, using C in Unix. Since it won't have more than 20 connections at a time, I figured I would use a thread per connection/socket. But the problem is writing to the sockets as I'll be sending user prompted msgs to clients. Once each socket is handled by a thread, how do I interact with the created thread to write to the sockets? Should each thread just read from the sockets and I'll write to sockets in the main program? Not sure if that's a good way to go about it.

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• Multiple complete HTTP requests stuck in TCP CLOSE_WAIT state

  - by Sean Owen

  I have a Java and Tomcat-based server application which initiates many outbound HTTP requests to other web sites. We use Jakarta's HTTP Core/Client libraries, very latest versions. The server locks up at some point since all its worker threads are stuck trying to close completed HTTP connections. Using 'lsof' reveals a bunch of sockets stuck in TCP CLOSE_WAIT state. This doesn't happen for all, or even most connections. In fact, I saw it before and resolved it by making sure to set the Connection: Close response header. So that makes me think it may be bad behavior of remote servers. It may have come up again since I moved the app to a totally new service provider -- different OS, network situation. But, I am still at a loss as to what I could do, if anything, to work around this. Some poking around on the internet didn't turn up anything I'm not already doing. Just thought I'd ask if anyone has seen and solved this?

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• WCF on Win Server 2008 and IIS7 with only net.tcp binding hide IIS features

  - by Nicola Celiento

  Hi all, I've installed HTTP Activation and Non-HTTP Activation IIS's features for Framework.NET 3.0 under WCF Activation feature. I'm trying to remove http and https bindings (under default Web Site) from IIS Manager and leave others (net.tcp, net.msmq, etc.) but if I close and re-open IIS manager I not found any icons in the right panel (Feature View). The only feature I see is IIS Manager Permissions. It's right I don't see them? I hope you can help me. Thank you in advance!

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• Tcp Socket Closed

  - by Michael Covelli

  I always thought that if you didn't implement a heartbeat, there was no way to know if one side of a TCP connection died unexpectedly. If the process was just killed on one side and didn't exit gracefully, there was no way for the socket to send FIN or let the other side know that it was closed. (See some of the comments here for example http://www.perlmonks.org/?node_id=566568 ) But there is a stock order server that I connect to that has a new "cancel all orders on disconnect feature" that cancels live orders if the client dis-connects. It works even when I kill the process on my end, and there is definitely no heartbeat from my app to it. So how is it able to detect when I've killed the process? My app is running on Windows Server 2003 and the order server is on Suse Linux Enterprise Server 10. Does Windows detect that the process associated with the socket is no longer alive and send the FIN?

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• Create multiple TCP Connections in C# then wait for data

  - by Ryan French

  Hi Everyone, I am currently creating a Windows Service that will create TCP connections to multiple machines (same socket on all machines) and then listen for 'events' from those machines. I am attempting to write the code to create a connection and then spawn a thread that listens to the connection waiting for packets from the machine, then decode the packets that come through, and call a function depending on the payload of the packet. The problem is I'm not entirely sure how to do that in C#. Does anyone have any helpful suggestions or links that might help me do this? Thanks in advance for any help!

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• [java] Threading socket handler for two sided communication in tcp port

  - by raven

  I want to make a chat which will be programed in java. one computer will host the server and the other one will initiate the socket [tcp port]. now from what I read there should be a loop that will constantly read the socket which means it will make the code stuck. I have a button that is 'actionperformed' on mouse release, I want to know if it will work along with the loops that constantly reads the socket so that it will also send the infromation I wrote. If I must thread it, I want to know if the run() method must be void because if I thread it it will mean creating a new class, and the whole GUI is one big class which includes a text area, and it's private. also how can I extract the information from the socket directly to the text area? lets say the textarea variable is called "chatOutput". thx :)

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• Secure password transmission over unencrypted tcp/ip

  - by academicRobot

  I'm in the designing stages of a custom tcp/ip protocol for mobile client-server communication. When not required (data is not sensitive), I'd like to avoid using SSL for overhead reasons (both in handshake latency and conserving cycles). My question is, what is the best practices way of transmitting authentication information over an unencrypted connection? Currently, I'm liking SRP or J-PAKE (they generate secure session tokens, are hash/salt friendly, and allow kicking into TLS when necessary), which I believe are both implemented in OpenSSL. However, I am a bit wary since I don't see many people using these algorithms for this purpose. Would also appreciate pointers to any materials discussing this topic in general, since I had trouble finding any.

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• Creating TCP network errors for unit testing

  - by Robert S. Barnes

  I'd like to create various network errors during testing. I'm using the Berkely sockets API directly in C++ on Linux. I'm running a mock server in another thread from within Boost.Test which listens on localhost. For instance, I'd like to create a timeout during connect. So far I've tried not calling accept in my mock server and setting the backlog to 1, then making multiple connections, but all seem to successfully connect. I would think that if there wasn't room in the backlog queue I would at least get a connection refused error if not a timeout. I'd like to do this all programatically if possible, but I'd consider using something external like IPchains to intentionally drop certain packets to certain ports during testing, but I'd need to automate creating and removing rules so I could do it from within my Boost.Test unit tests. I suppose I could mock the various system calls involved, but I'd rather go through a real TCP stack if possible. Ideas?

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• who uses a TCP port?

  - by dijxtra

  One of gen_servers in my app call gen_tcp:listen(Port, [{active, true}]). First time I run unit test, it returns {ok, Socket}, but second time I run the same unit test, it returns an {error, eaddrinuse}, but lsof -i TCP returns nothing. Also, when the same unit_test is run twice on another machine (WinXP), it works as expected (that is, returns {ok, Socket} both times). Therefore, my gen_server obviously releases the port, but Erlang somehow doesn't know that. So, how can I figure out who does Erlang think uses this address?

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• TCP Scanner Python MultiThreaded

  - by user1473508

  I'm trying to build a small tcp scanner for a netmask. The code is as follow: import socket,sys,re,struct from socket import * host = sys.argv[1] def RunScanner(host): s = socket(AF_INET, SOCK_STREAM) s.connect((host,80)) s.settimeout(0.1) String = "GET / HTTP/1.0" s.send(String) data = s.recv(1024) if data: print "host: %s have port 80 open"%(host) Slash = re.search("/", str(host)) if Slash : netR,_,Wholemask = host.partition('/') Wholemask = int(Wholemask) netR = struct.unpack("!L",inet_aton(netR))[0] for host in (inet_ntoa(struct.pack("!L", netR+n)) for n in range(0, 1<<32-Wholemask)): try: print "Doing host",host RunScanner(host) except: pass else: RunScanner(host) To launch : python script.py 10.50.23.0/24 The problem I'm having is that even with a ridiculous low settimeout value set, it takes ages to cover the 255 ip addresses since most of them are not assigned to a machine. How can i make a way faster scanner that wont get stuck if the port is close.MultiThreading ? Thanks !

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• Indy Write Buffering / Efficient TCP communication

  - by Smasher

  I know, I'm asking a lot of questions...but as a new delphi developer I keep falling over all these questions :) This one deals with TCP communication using indy 10. To make communication efficient, I code a client operation request as a single byte (in most scenarios followed by other data bytes of course, but in this case only one single byte). Problem is that var Bytes : TBytes; ... SetLength (Bytes, 1); Bytes [0] := OpCode; FConnection.IOHandler.Write (Bytes, 1); ErrorCode := Connection.IOHandler.ReadByte; does not send that byte immediately (at least the servers execute handler is not invoked). If I change the '1' to a '9' for example everything works fine. I assumed that Indy buffers the outgoing bytes and tried to disable write buffering with FConnection.IOHandler.WriteBufferClose; but it did not help. How can I send a single byte and make sure that it is immediatly sent? And - I add another little question here - what is the best way to send an integer using indy? Unfortunately I can't find function like WriteInteger in the IOHandler of TIdTCPServer...and WriteLn (IntToStr (SomeIntVal)) seems not very efficient to me. Does it make a difference whether I use multiple write commands in a row or pack things together in a byte array and send that once? Thanks for any answers! EDIT: I added a hint that I'm using Indy 10 since there seem to be major changes concerning the read and write procedures.

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• RDP through TCP Proxy

  - by johng100

  Hi, First time in Stackoverflow and I'm hoping someone can help me. I'm looking at a proof of concept to pass RDP traffic through a TCP Proxy/tunnel which will pass through firewalls using HTTPS. The problem has to do with deploying images to machines and so it can't be assumed that the .NET framework will be present, so C++ is being used at the deployment end of a connection. The basic system I have at present is a program which listens for client connections on a port then passes any data to a WCF service which stores it as a byte array. A deployment machine (using GSoap and C++) polls the WCF service for messages and if it finds them then passes the data onto the target server process via sockets. I know this sounds horrible, but it works for simple test clients and server passing data to and from simple test client and server programs via this WCF/C++/C# proxy layer. But I have to support traffic from RDP, VNC and possibly others, so I need a transparent proxy to do this and am wondering whether the above approach is worth pursuing. I've read up on SSH tunneling and that seems a possibility. My basic question is is it possible to tunnel RDP traffic over HTTPS using custom code. Thanks John

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• Decoding tcp packets using python

  - by mikip

  Hello I am trying to decode data received over a tcp connection. The packets are small, no more than 100 bytes. However when there is a lot of them I receive some of the the packets joined together. Is there a way to prevent this. I am using python I have tried to separate the packets, my source is below. The packets start with STX byte and end with ETX bytes, the byte following the STX is the packet length, (packet lengths less than 5 are invalid) the checksum is the last bytes before the ETX def decode(data): while True: start = data.find(STX) if start == -1: #no stx in message pkt = '' data = '' break #stx found , next byte is the length pktlen = ord(data[1]) #check message ends in ETX (pktken -1) or checksum invalid if pktlen < 5 or data[pktlen-1] != ETX or checksum_valid(data[start:pktlen]) == False: print "Invalid Pkt" data = data[start+1:] continue else: pkt = data[start:pktlen] data = data[pktlen:] break return data , pkt I use it like this #process reports try: data = sock.recv(256) except: continue else: while data: data, pkt = decode(data) if pkt: process(pkt) Also if there are multiple packets in the data stream, is it best to return the packets as a collection of lists or just return the first packet I am not that familiar with python, only C, is this method OK. Any advice would be most appreciated. Thanks in advance Thanks

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• Limit TCP requests per IP

  - by asmo

  Hello! I'm wondering how to limit the TCP requests per client (per specific IP) in Java. For example, I would like to allow a maximum of X requests per Y seconds for each client IP. I thought of using static Timer/TimerTask in combination with a HashSet of temporary restricted IPs. private static final Set<InetAddress> restrictedIPs = Collections.synchronizedSet(new HashSet<InetAddress>()); private static final Timer restrictTimer = new Timer(); So when a user connects to the server, I add his IP to the restricted list, and start a task to unrestrict him in X seconds. restrictedIPs.add(socket.getInetAddress()); restrictTimer.schedule(new TimerTask() { public void run() { restrictedIPs.remove(socket.getInetAddress()); } }, MIN_REQUEST_INTERVAL); My problem is that at the time the task will run, the socket object may be closed, and the remote IP address won't be accessible anymore... Any ideas welcomed! Also, if someone knows a Java-framework-built-in way to achieve this, I'd really like to hear it.

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• Why does my Perl TCP server script hang with many TCP connections?

  - by viraptor

  I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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• Listening UDP or switch to TCP in a MFC application

  - by Alexander.S

  I'm editing a legacy MFC application, and I have to add some basic network functionalities. The operating side has to receive a simple instruction (numbers 1,2,3,4...) and do something based on that. The clients wants the latency to be as fast as possible, so naturally I decided to use datagrams (UDP). But reading all sorts of resources left me bugged. I cannot listen to UDP sockets (CAsyncSocket) in MFC, it's only possible to call Receive which blocks and waits. Blocking the UI isn't really a smart. So I guess I could use some threading technique, but since I'm not all that experienced with MFC how should that be implemented? The other part of the question is should I do this, or revert to TCP, considering reliability and implementation issues. I know that UDP is unreliable, but just how unreliable is it really? I read that it is up to 50% faster, which is a lot for me. References I used: http://msdn.microsoft.com/en-us/library/09dd1ycd(v=vs.80).aspx

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• Sending arbitrarily long string over Java TCP socket

  - by bibismcbryde

  I have an Android app that communicates over a TCP socket with a server I wrote. The method I'm using now to read and write output works fine for smaller strings (up to 60kB) but I get an exception thrown when the string is much longer than that. Here is the relevant part of what I have for the server and client: Server: DataInputStream dis = null; DataOutputStream dos = null; try { dis = new DataInputStream(server.getInputStream()); dos = new DataOutputStream(server.getOutputStream()); String input = ""; input = dis.readUTF(); handle_input info = new handle_input(input, id); String xml = info.handle(); dos.writeUTF(xml); server.close(); } Client: Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; Boolean result; try { socket = new Socket(ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(the_text); String in = ""; while (in.equals("")) { in += dis.readUTF(); } } How can I modify it to deal with potentially enormous Strings? I've been looking around and can't seem to find a clear answer. Thanks.

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• non blocking TCP-acceptor not reading from socket

  - by Abruzzo Forte e Gentile

  I have the code below implementing a NON-Blocking TCP acceptor. Clients are able to connect without any problem and the writing seems occurring as well, but the acceptor doesn't read anything from the socket and the call to read() blocks indefinitely. Am I using some wrong setting for the acceptor? Kind Regards AFG int main(){ create_programming_socket(); poll_programming_connect(); while(1){ poll_programming_read(); } } int create_programming_socket(){ int cnt = 0; p_listen_socket = socket( AF_INET, SOCK_STREAM, 0 ); if( p_listen_socket < 0 ){ return 1; } int flags = fcntl( p_listen_socket, F_GETFL, 0 ); if( fcntl( p_listen_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ return 1; } bzero( (char*)&p_serv_addr, sizeof(p_serv_addr) ); p_serv_addr.sin_family = AF_INET; p_serv_addr.sin_addr.s_addr = INADDR_ANY; p_serv_addr.sin_port = htons( p_port ); if( bind( p_listen_socket, (struct sockaddr*)&p_serv_addr , sizeof(p_serv_addr) ) < 0 ) { return 1; } listen( p_listen_socket, 5 ); return 0; } int poll_programming_connect(){ int retval = 0; static socklen_t p_clilen = sizeof(p_cli_addr); int res = accept( p_listen_socket, (struct sockaddr*)&p_cli_addr, &p_clilen ); if( res > 0 ){ p_conn_socket = res; int flags = fcntl( p_conn_socket, F_GETFL, 0 ); if( fcntl( p_conn_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ retval = 1; }else{ p_connected = true; } }else if( res == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): accept(c_listen_socket) would block\n"); }else{ retval = 1; } return retval; } int poll_programming_read(){ int retval = 0; bzero( p_buffer, 256 ); int numbytes = read( p_conn_socket, p_buffer, 255 ); if( numbytes > 0 ) { fprintf( stderr, "poll_sock(): read() read %d bytes\n", numbytes ); pkt_struct2_t tx_buf; int fred; int i; } else if( numbytes == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): read() would block\n"); } else { close( p_conn_socket ); p_connected = false; retval = 1; } return retval; }

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• Centos does not open port/s after the rule/s are appended

  - by Charlie Dyason

  So after some battling and struggling with the firewall, i see that I may be doing something or the firewall isnt responding correctly there is has a port filter that is blocking certain ports. by the way, I have combed the internet, posted on forums, done almost everything and now hence the website name "serverfault", is my last resort, I need help What I hoped to achieve is create a pptp server to connect to with windows/linux clients UPDATED @ bottom Okay, here is what I did: I made some changes to my iptables file, giving me endless issues and so I restored the iptables.old file contents of iptables.old: # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT after iptables.old restore(back to stock), nmap scan shows: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 13:54 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.014s latency). Not shown: 997 filtered ports PORT STATE SERVICE 22/tcp open ssh 113/tcp closed ident 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 4.95 seconds if I append rule: (to accept all tcp ports incoming to server on interface eth0) iptables -A INPUT -i eth0 -m tcp -j ACCEPT nmap output: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 13:58 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.017s latency). Not shown: 858 filtered ports, 139 closed ports PORT STATE SERVICE 22/tcp open ssh 443/tcp open https 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 3.77 seconds *notice it allows and opens port 443 but no other ports, and it removes port 113...? removing previous rule and if I append rule: (allow and open port 80 incoming to server on interface eth0) iptables -A INPUT -i eth0 -m tcp -p tcp --dport 80 -j ACCEPT nmap output: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 14:01 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.014s latency). Not shown: 996 filtered ports PORT STATE SERVICE 22/tcp open ssh 80/tcp closed http 113/tcp closed ident 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 5.12 seconds *notice it removes port 443 and allows 80 but is closed without removing previous rule and if I append rule: (allow and open port 1723 incoming to server on interface eth0) iptables -A INPUT -i eth0 -m tcp -p tcp --dport 1723 -j ACCEPT nmap output: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 14:05 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.015s latency). Not shown: 996 filtered ports PORT STATE SERVICE 22/tcp open ssh 80/tcp closed http 113/tcp closed ident 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 5.16 seconds *notice no change in ports opened or closed??? after removing rules: iptables -A INPUT -i eth0 -m tcp -p tcp --dport 80 -j ACCEPT iptables -A INPUT -i eth0 -m tcp -p tcp --dport 1723 -j ACCEPT nmap output: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 14:07 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.015s latency). Not shown: 998 filtered ports PORT STATE SERVICE 22/tcp open ssh 113/tcp closed ident Nmap done: 1 IP address (1 host up) scanned in 5.15 seconds and returning rule: (to accept all tcp ports incoming to server on interface eth0) iptables -A INPUT -i eth0 -m tcp -j ACCEPT nmap output: nmap [server ip] Starting Nmap 6.00 ( nmap.org ) at 2013-11-01 14:07 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.017s latency). Not shown: 858 filtered ports, 139 closed ports PORT STATE SERVICE 22/tcp open ssh 443/tcp open https 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 3.87 seconds notice the eth0 changes the 999 filtered ports to 858 filtered ports, 139 closed ports QUESTION: why cant I allow and/or open a specific port, eg. I want to allow and open port 443, it doesnt allow it, or even 1723 for pptp, why am I not able to??? sorry for the layout, the editor was give issues (aswell... sigh) UPDATE @Madhatter comment #1 thank you madhatter in my iptables file: # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i eth0 -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT # ----------all rules mentioned in post where added here ONLY!!!---------- -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT if I want to allow and open port 1723 (or edit iptables to allow a pptp connection from remote pc), what changes would I make? (please bear with me, my first time working with servers, etc.) Update MadHatter comment #2 iptables -L -n -v --line-numbers Chain INPUT (policy ACCEPT 0 packets, 0 bytes) num pkts bytes target prot opt in out source destination 1 9 660 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 2 0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 3 0 0 ACCEPT all -- eth0 * 0.0.0.0/0 0.0.0.0/0 4 0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 5 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 6 0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) num pkts bytes target prot opt in out source destination 1 0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited Chain OUTPUT (policy ACCEPT 6 packets, 840 bytes) num pkts bytes target prot opt in out source destination just on a personal note, madhatter, thank you for the support , I really appreciate it! UPDATE MadHatter comment #3 here are the interfaces ifconfig eth0 Link encap:Ethernet HWaddr 00:1D:D8:B7:1F:DC inet addr:[server ip] Bcast:[server ip x.x.x].255 Mask:255.255.255.0 inet6 addr: fe80::21d:d8ff:feb7:1fdc/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:36692 errors:0 dropped:0 overruns:0 frame:0 TX packets:4247 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2830372 (2.6 MiB) TX bytes:427976 (417.9 KiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.8.0.1 P-t-P:10.8.0.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) remote nmap nmap -p 1723 [server ip] Starting Nmap 6.00 ( http://nmap.org ) at 2013-11-01 16:17 SAST Nmap scan report for server.address.net ([server ip]) Host is up (0.017s latency). PORT STATE SERVICE 1723/tcp filtered pptp Nmap done: 1 IP address (1 host up) scanned in 0.51 seconds local nmap nmap -p 1723 localhost Starting Nmap 5.51 ( http://nmap.org ) at 2013-11-01 16:19 SAST Nmap scan report for localhost (127.0.0.1) Host is up (0.000058s latency). Other addresses for localhost (not scanned): 127.0.0.1 PORT STATE SERVICE 1723/tcp open pptp Nmap done: 1 IP address (1 host up) scanned in 0.11 seconds UPDATE MadHatter COMMENT POST #4 I apologize, if there might have been any confusion, i did have the rule appended: (only after 3rd post) iptables -A INPUT -p tcp --dport 1723 -j ACCEPT netstat -apn|grep -w 1723 tcp 0 0 0.0.0.0:1723 0.0.0.0:* LISTEN 1142/pptpd There are not VPN's and firewalls between the server and "me" UPDATE MadHatter comment #5 So here is an intersting turn of events: I booted into windows 7, created a vpn connection, went through the verfication username & pword - checking the sstp then checking pptp (went through that very quickly which meeans there is no problem), but on teh verfication of username and pword (before registering pc on network), it got stuck, gave this error Connection failed with error 2147943625 The remote computer refused the network connection netstat -apn | grep -w 1723 before connecting: netstat -apn |grep -w 1723 tcp 0 0 0.0.0.0:1723 0.0.0.0:* LISTEN 1137/pptpd after the error came tried again: netstat -apn |grep -w 1723 tcp 0 0 0.0.0.0:1723 0.0.0.0:* LISTEN 1137/pptpd tcp 0 0 41.185.26.238:1723 41.13.212.47:49607 TIME_WAIT - I do not know what it means but seems like there is progress..., any thoughts???

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• send multiple file over TCP with C# using TcpClient

  - by xnoor

  I'm trying to send multiple files over TCP using C# TcpClient, for a single file it works great, but when I have multiple files, it sends only the first one. Here is my code: SENDING FILES try { TcpClient tcpClient = new TcpClient(); NetworkStream networkStream; FileStream fileStream = null; tcpClient.Connect(appUpdateMessage.receiverIpAddress, 12000); networkStream = tcpClient.GetStream(); byte[] byteSend = new byte[tcpClient.ReceiveBufferSize]; string startupPath = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase).Substring(6); DirectoryInfo directoriesInfo = new DirectoryInfo(startupPath); DirectoryInfo[] directories = directoriesInfo.GetDirectories(); FileInfo[] files = directoriesInfo.GetFiles(); for (int iLoop = 0; iLoop < directories.Length; iLoop++) { FileInfo[] subdirectoryFiles = directories[iLoop].GetFiles(); foreach (FileInfo fi in subdirectoryFiles) { fileStream = new FileStream(fi.FullName, FileMode.Open, FileAccess.Read); BinaryReader binFile = new BinaryReader(fileStream); FileUpdateMessage fileUpdateMessage = new FileUpdateMessage(); fileUpdateMessage.fileName = fi.Name; fileUpdateMessage.fileSize = fi.Length; fileUpdateMessage.targetDirectory = fi.Directory.Name; MessageContainer messageContainer = new MessageContainer(); messageContainer.messageType = MessageType.FileProperties; messageContainer.messageContnet = SerializationManager.XmlFormatterObjectToByteArray(fileUpdateMessage); byte[] messageByte = SerializationManager.XmlFormatterObjectToByteArray(messageContainer); networkStream.Write(messageByte, 0, messageByte.Length); int bytesSize = 0; byte[] downBuffer = new byte[2048]; while ((bytesSize = fileStream.Read(downBuffer, 0, downBuffer.Length)) > 0) { networkStream.Write(downBuffer, 0, bytesSize); } fileStream.Close(); } } tcpClient.Close(); networkStream.Close(); return true; } catch (Exception ex) { //logger.Info(ex.Message); return false; } finally { } RECEIVING FILES try { TcpClient tcpClient = c as TcpClient; NetworkStream networkstream = tcpClient.GetStream(); FileStream fileStream = null; byte[] _data = new byte[1024]; int _bytesRead = 0; _bytesRead = networkstream.Read(_data, 0, _data.Length); MessageContainer messageContainer = new MessageContainer(); messageContainer = SerializationManager.XmlFormatterByteArrayToObject(_data, messageContainer) as MessageContainer; switch (messageContainer.messageType) { case MessageType.FileProperties: FileUpdateMessage fileUpdateMessage = new FileUpdateMessage(); fileUpdateMessage = SerializationManager.XmlFormatterByteArrayToObject(messageContainer.messageContnet, fileUpdateMessage) as FileUpdateMessage; string startupPath = @"d:updatefolder";//System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().GetName().CodeBase).Substring(6); DirectoryInfo mainDirectory = new DirectoryInfo(startupPath); DirectoryInfo targetDirecotry = new DirectoryInfo(startupPath + "\\" + fileUpdateMessage.targetDirectory); if (!targetDirecotry.Exists) { mainDirectory.CreateSubdirectory(fileUpdateMessage.targetDirectory); } fileStream = new FileStream(startupPath + "\\" + fileUpdateMessage.targetDirectory + "\\" + fileUpdateMessage.fileName, FileMode.Create, FileAccess.Write, FileShare.ReadWrite); long filezie = fileUpdateMessage.fileSize; int byteSize = 0; byte[] downBuffer = new byte[2048]; while ((byteSize = networkstream.Read(downBuffer, 0, downBuffer.Length)) > 0) { fileStream.Write(downBuffer, 0, byteSize); if (this.InvokeRequired) { this.Invoke((MethodInvoker)delegate { //progressBar1.Value = Convert.ToInt32((byteSize * 100) / fileUpdateMessage.fileSize); progressBar1.Value = Convert.ToInt32((fileStream.Length * 100) / fileUpdateMessage.fileSize); lblFileName.Text = fileUpdateMessage.fileName; }); } else { //progressBar1.Value = Convert.ToInt32((byteSize * 100) / fileUpdateMessage.fileSize); lblFileName.Text = fileUpdateMessage.fileName; } } fileStream.Close(); networkstream.Close(); break; } } catch (Exception ex) { //logger.Error(ex.Message); } Any idea what I am doing wrong?

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• Ports do not open after rules appended in iptables

  - by user2699451

  I have a server that I am trying to setup for OpenVPN. I have followed all the steps, but I see that when I try to connect to it in Windows, it doesn't allow me, it just hangs on connecting, so I did a nmap scan and I see that port 1194 is not open so naturally I append the rule to open 1194 with: iptables -A INPUT -i eth0 -p tcp --dport 1194 -j ACCEPT followed by service iptables save and service iptables restart which all executed successfully. Then I try again, but it doesn't work and another nmap scan says that port 1194 is closed. Here is the iptables configuration: # Generated by iptables-save v1.4.7 on Thu Oct 31 09:47:38 2013 *nat :PREROUTING ACCEPT [27410:3091993] :POSTROUTING ACCEPT [0:0] :OUTPUT ACCEPT [5042:376160] -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -j SNAT --to-source 41.185.26.238 -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE COMMIT # Completed on Thu Oct 31 09:47:38 2013 # Generated by iptables-save v1.4.7 on Thu Oct 31 09:47:38 2013 *filter :INPUT ACCEPT [23571:2869068] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [27558:3656524] :vl - [0:0] -A INPUT -p tcp -m tcp --dport 5252 -m comment --comment "SSH Secure" -j ACCEPT -A INPUT -p icmp -m icmp --icmp-type 8 -m state --state NEW,RELATED,ESTABLISHED -$ -A INPUT -i lo -j ACCEPT -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -m comment --comment "SSH" -j ACCEPT -A INPUT -p tcp -m tcp --dport 80 -m comment --comment "HTTP" -j ACCEPT -A INPUT -p tcp -m tcp --dport 8080 -m comment --comment "HTTPS" -j ACCEPT -A INPUT -p tcp -m tcp --dport 443 -m comment --comment "HTTP Encrypted" -j ACCEP$ -A INPUT -i eth0 -p tcp -m tcp --dport 1723 -j ACCEPT -A INPUT -i eth0 -p gre -j ACCEPT -A INPUT -p udp -m udp --dport 1194 -j ACCEPT -A FORWARD -i ppp+ -o eth0 -j ACCEPT -A FORWARD -i eth0 -o ppp+ -j ACCEPT -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 10.8.0.0/24 -j ACCEPT -A FORWARD -j REJECT --reject-with icmp-port-unreachable -A OUTPUT -p icmp -m icmp --icmp-type 0 -m state --state RELATED,ESTABLISHED -j A$ COMMIT # Completed on Thu Oct 31 09:47:38 2013 and my nmap scan from: localhost: nmap localhost Starting Nmap 5.51 ( http://nmap.org ) at 2013-10-31 09:53 SAST Nmap scan report for localhost (127.0.0.1) Host is up (0.000011s latency). Other addresses for localhost (not scanned): 127.0.0.1 Not shown: 996 closed ports PORT STATE SERVICE 22/tcp open ssh 25/tcp open smtp 443/tcp open https 1723/tcp open pptp Nmap done: 1 IP address (1 host up) scanned in 0.06 seconds remote pc: nmap [server ip] Starting Nmap 6.00 ( http://nmap.org ) at 2013-10-31 09:53 SAST Nmap scan report for rla04-nix1.wadns.net (41.185.26.238) Host is up (0.025s latency). Not shown: 858 filtered ports, 139 closed ports PORT STATE SERVICE 22/tcp open ssh 443/tcp open https 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 15.70 seconds So, I do not know what is causing this, any assistance will be appreciated! UPDATE AFTER FIRST ANSWER::: [root@RLA04-NIX1 ~]# iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT [root@RLA04-NIX1 ~]# iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT [root@RLA04-NIX1 ~]# iptables -A FORWARD -j REJECT [root@RLA04-NIX1 ~]# iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE [root@RLA04-NIX1 ~]# service iptables save iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ] [root@RLA04-NIX1 ~]# service iptables restart iptables: Flushing firewall rules: [ OK ] iptables: Setting chains to policy ACCEPT: filter nat [ OK ] iptables: Unloading modules: [ OK ] iptables: Applying firewall rules: [ OK ] [root@RLA04-NIX1 ~]# lsof -i :1194 -bash: lsof: command not found iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:5252 /* SSH Secure */ ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 8 state NEW,RELATED,ESTABLISHED ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 /* SSH */ ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 /* HTTP */ ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 /* HTTPS */ ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443 /* HTTP Encrypted */ ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:1723 ACCEPT 47 -- 0.0.0.0/0 0.0.0.0/0 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:1194 Chain FORWARD (policy ACCEPT) target prot opt source destination ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED ACCEPT all -- 10.8.0.0/24 0.0.0.0/0 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED ACCEPT all -- 10.8.0.0/24 0.0.0.0/0 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-port-unreachable Chain OUTPUT (policy ACCEPT) target prot opt source destination ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 icmp type 0 state RELATED,ESTABLISHED Chain vl (0 references) target prot opt source destination [root@RLA04-NIX1 ~]# nmap localhostt Starting Nmap 5.51 ( http://nmap.org ) at 2013-10-31 11:13 SAST remote pc nmap [server ip] Starting Nmap 6.00 ( http://nmap.org ) at 2013-10-31 11:11 SAST Nmap scan report for rla04-nix1.wadns.net (41.185.26.238) Host is up (0.020s latency). Not shown: 858 filtered ports, 139 closed ports PORT STATE SERVICE 22/tcp open ssh 443/tcp open https 8008/tcp open http Nmap done: 1 IP address (1 host up) scanned in 4.18 seconds localhost nmap localhost Starting Nmap 5.51 ( http://nmap.org ) at 2013-10-31 11:13 SAST Nmap scan report for localhost (127.0.0.1) Host is up (0.000011s latency). Other addresses for localhost (not scanned): 127.0.0.1 Not shown: 996 closed ports PORT STATE SERVICE 22/tcp open ssh 25/tcp open smtp 443/tcp open https 1723/tcp open pptp Nmap done: 1 IP address (1 host up) scanned in 0.06 seconds UPDATE AFTER SCANNING UDP PORTS Sorry, I am noob, I am still learning, but here is the output for: nmap -sU [server ip] Starting Nmap 6.00 ( http://nmap.org ) at 2013-10-31 11:33 SAST Nmap scan report for [server address] ([server ip]) Host is up (0.021s latency). Not shown: 997 open|filtered ports PORT STATE SERVICE 53/udp closed domain 123/udp closed ntp 33459/udp closed unknown Nmap done: 1 IP address (1 host up) scanned in 8.57 seconds btw, no changes have been made since post started (except for iptables changes)

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• TCP client in C and server in Java

  - by faldren

  I would like to communicate with 2 applications : a client in C which send a message to the server in TCP and the server in Java which receive it and send an acknowledgement. Here is the client (the code is a thread) : static void *tcp_client(void *p_data) { if (p_data != NULL) { char const *message = p_data; int sockfd, n; struct sockaddr_in serv_addr; struct hostent *server; char buffer[256]; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) { error("ERROR opening socket"); } server = gethostbyname(ALARM_PC_IP); if (server == NULL) { fprintf(stderr,"ERROR, no such host\n"); exit(0); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length); serv_addr.sin_port = htons(TCP_PORT); if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) { error("ERROR connecting"); } n = write(sockfd,message,strlen(message)); if (n < 0) { error("ERROR writing to socket"); } bzero(buffer,256); n = read(sockfd,buffer,255); if (n < 0) { error("ERROR reading from socket"); } printf("Message from the server : %s\n",buffer); close(sockfd); } return 0; } And the java server : try { int port = 9015; ServerSocket server=new ServerSocket(port); System.out.println("Server binded at "+((server.getInetAddress()).getLocalHost()).getHostAddress()+":"+port); System.out.println("Run the Client"); while (true) { Socket socket=server.accept(); BufferedReader in= new BufferedReader(new InputStreamReader(socket.getInputStream())); System.out.println(in.readLine()); PrintStream out=new PrintStream(socket.getOutputStream()); out.print("Welcome by server\n"); out.flush(); out.close(); in.close(); System.out.println("finished"); } } catch(Exception err) { System.err.println("* err"+err); } With n = read(sockfd,buffer,255); the client is waiting a response and for the server, the message is never ended so it doesn't send a response with PrintStream. If I remove these lines : bzero(buffer,256); n = read(sockfd,buffer,255); if (n < 0) { error("ERROR reading from socket"); } printf("Message from the server : %s\n",buffer); The server knows that the message is finished but the client can't receive the response. How solve that ? Thank you

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• HA Proxy Stick-table and tcp-connection configuration

  - by Vladimir

  I am using HA Proxy HA-Proxy version 1.4.18 2011/09/16 I am trying to insert the following into /etc/init.d/haproxy.cfg file # Use General Purpose Couter (gpc) 0 in SC1 as a global abuse counter # Monitors the number of request sent by an IP over a period of 10 seconds stick-table type ip size 1m expire 10s store gpc0,http_req_rate(10s) tcp-request connection track-sc1 src tcp-request connection reject if { src_get_gpc0 gt 0 } # Table definition stick-table type ip size 100k expire 30s store conn_cur(3s) # Allow clean known IPs to bypass the filter tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst } # Shut the new connection as long as the client has already 10 opened tcp-request connection reject if { src_conn_cur ge 10 } tcp-request connection track-sc1 src I get the following error: [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:36] : stick-table: unknown argument 'store'. [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:37] : unknown argument 'connection' after 'tcp-request' in proxy 'http_proxy' [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:38] : unknown argument 'connection' after 'tcp-request' in proxy 'http_proxy' [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:41] : stick-table: unknown argument 'store'. [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:43] : unknown argument 'connection' after 'tcp-request' in proxy 'http_proxy' [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:45] : unknown argument 'connection' after 'tcp-request' in proxy 'http_proxy' [ALERT] 256/113143 (4627) : parsing [/etc/haproxy/haproxy.cfg:46] : unknown argument 'connection' after 'tcp-request' in proxy 'http_proxy' [ALERT] 256/113143 (4627) : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg [WARNING] 256/113143 (4627) : Proxy 'http_proxy': in multi-process mode, stats will be limited to process assigned to the current request. [ALERT] 256/113143 (4627) : Fatal errors found in configuration. [fail] Could you please tell me what is wrong with the code? Thanks!

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