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  • C automatically assign port

    - by Gary
    Hi, I just wanted to know how to use C to automatically assign a free port (and see what was used) if a specific port number is not provided. For example, i'm using this: struct sockaddr_in address; address->sin_family = AF_INET; address->sin_addr.s_addr = INADDR_ANY; address->sin_port = htons( port ); But how can I replace the sin_port assignment and let C automatically assign for me? Thanks!

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  • Community "Groups" feature (Ruby on Rails)

    - by timstepp
    Are there any good examples/plugins that enable users to create groups within a community application. For example, I would like to create a Group class and add it to something like Community Engine (http://communityengine.org/). Essentially, users need to be able to create and manage groups that other users can join (much like Facebook Pages). Thanks!

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  • android ftp upload has stopped error

    - by Goxel Arp
    class Asenkron extends AsyncTask<String,Integer,Long> { @Override protected Long doInBackground(String... aurl) { FTPClient con=null; try ` { con = new FTPClient(); con.connect(aurl[0]); if (con.login(aurl[1], aurl[2])) { con.enterLocalPassiveMode(); // important! con.setFileType(http://FTP.BINARY_FILE_TYPE); FileInputStream in = new FileInputStream(new File(aurl[3])); boolean result = con.storeFile(aurl[3], in); in.close(); con.logout(); con.disconnect(); } } catch (Exception e) { Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_LONG).show(); } return null; } protected void onPostExecute(String result) {} } I AM USING THIS CLASS LIKE BELOW.THERE IS BUTTON AND WHENEVER I CLICK THE BUTTON IT SHOULD START FTP UPLOAD PROCESS IN BACKGROUND BUT I GET "PROGRAM HAS STOPPED UNFORTUNATELY" ERROR. Assume that The ftp address and username password pathfile sections are true and I get the internet and network permissions already by the way ... button1.setOnClickListener(new OnClickListener() { public void onClick(View arg0) { new Asenkron().execute("ftpaddress","username","pass","pathfileon telephone"); } }); And here is the logcat for you to analyse the potential error and help me ... 10-13 13:01:25.591: I/dalvikvm(633): threadid=3: reacting to signal 3 10-13 13:01:25.711: I/dalvikvm(633): Wrote stack traces to '/data/anr/traces.txt' 10-13 13:01:25.921: D/gralloc_goldfish(633): Emulator without GPU emulation detected. 10-13 13:01:31.441: W/dalvikvm(633): threadid=11: thread exiting with uncaught exception (group=0x409c01f8) 10-13 13:01:31.461: E/AndroidRuntime(633): FATAL EXCEPTION: AsyncTask #1 10-13 13:01:31.461: E/AndroidRuntime(633): java.lang.RuntimeException: An error occured while executing doInBackground() 10-13 13:01:31.461: E/AndroidRuntime(633): at android.os.AsyncTask$3.done(AsyncTask.java:278) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 10-13 13:01:31.461: E/AndroidRuntime(633): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.lang.Thread.run(Thread.java:856) 10-13 13:01:31.461: E/AndroidRuntime(633): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 10-13 13:01:31.461: E/AndroidRuntime(633): at android.os.Handler.<init>(Handler.java:121) 10-13 13:01:31.461: E/AndroidRuntime(633): at android.widget.Toast$TN.<init>(Toast.java:317) 10-13 13:01:31.461: E/AndroidRuntime(633): at android.widget.Toast.<init>(Toast.java:91) 10-13 13:01:31.461: E/AndroidRuntime(633): at android.widget.Toast.makeText(Toast.java:233) 10-13 13:01:31.461: E/AndroidRuntime(633): at com.example.ftpodak.ODAK$Asenkron.doInBackground(ODAK.java:74) 10-13 13:01:31.461: E/AndroidRuntime(633): at com.example.ftpodak.ODAK$Asenkron.doInBackground(ODAK.java:1) 10-13 13:01:31.461: E/AndroidRuntime(633): at android.os.AsyncTask$2.call(AsyncTask.java:264) 10-13 13:01:31.461: E/AndroidRuntime(633): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 10-13 13:01:31.461: E/AndroidRuntime(633): ... 5 more By the way I changed the relevant code like that ; instead of catch (Exception e) { Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_LONG).show(); } I replaced with this code catch (Exception e) { HATA=e.toString(); } And I added the code to button textview1.setText(HATA); So I can see the error on the textview and it is writing that "Android java.net.UnknownHostException: Host is unresolved" But i know that the ftp server is correct and I check the ftp server from the AndFTP application. With the same address login and pass information ftp server is working.So the problem is in my code I think.Any help will be too much appreciated.Anyone who can help me I can give teamviewer to analyse what is the problem ...

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  • Can an application affect TCP retransmits

    - by sipwiz
    I'm troubleshooting some communications issues and in the network traces I am occasionally coming across TCP sequence errors. One example I've got is: Server to Client: Seq=3174, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3224, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3274, Len=10 Client to Server: Ack=3224, SLE=3274, SRE=3284 Packets 4 & 5 are recorded in the trace (which is from a router in between the client and server) at almost exactly the same time so they most likely crossed in transit. The TCP session has got out of sync with the client missing the last two transmissions from the server. Those two packets should have been retransmitted but they weren't, the next log in the trace is a RST packet from the Client 24 seconds after packet 6. My question is related to what could be responsible for the failure to retransmit the server data from packets 3 & 5? I would assume that the retransmit would be at the operating system level but is there anyway the application could influence it and stop it being sent? A thread blocking or put to sleep or something like that?

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  • What's pcap_pkthdr there for?

    - by httpinterpret
    Code snippet from here: void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data) { .... /* retireve the position of the ip header */ ih = (ip_header *) (pkt_data + 14); //length of ethernet header .... What's const struct pcap_pkthdr *header for, when do we need it, how is it populated (since there is no such info in the packet itself as below)?

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  • Ubuntu problem not connecting to wireless or wired network

    - by ToughPal
    I recently installed openvpn and things were working. But I got a weird screen after a few hours and on restart my wired and wireless connections are not working. Can someone help? cat /etc/network/interfaces auto lo iface lo inet loopback cat /etc/resolv.conf #Generated by NetworkManager Is there anything missing? I tried both wired and wireless and both are not working. Usually if I ever have a problem with wireless, the wired always work! My /etc/network/interfaces is looking wrong. Can you please send me yours? I am using ubuntu 9.10 and the internet was working correctly until today! Please help

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  • On a local network, are you able to password protect certain folders and how (in windows xp)?

    - by Derek
    I have a local network set up for my small office which consists of me, the manager, my wife, the secretary, and a few sales people/others. I would like to share passwords over the network and other such things privately to my wife, the secretary, but would not like the sales people and others to have access to it, yet I need the others to have access to other folders/documents that I'd like to share. How would I go about doing this if not by password? Thanks in advance

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  • Basic Client-Server Design for persistent connections?

    - by cam
    Here's as far as I understand it: Client & Server make connection Client sends server data Server interprets data, sends client data So on, and so forth, until client sends disconnect signal. I'm just wondering about implementation. Step 2 and 3 are confusing to me, maybe I'm over-complicating it. Is there anymore to interpreting the data than a giant switch statement? Any good books on client/server design? Specifically talking about multithreaded servers, scalability, and message design (byte 1 = header info, byte 2 = blah blah, etc)? Specifically geared towards C++.

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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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  • need for tcp fine-tuning on heavily used proxy server

    - by Vijay Gharge
    Hi all, I am using squid like Internet proxy server on RHEL 4 update 6 & 8 with quite heavy load i.e. 8k established connections during peak hour. Without depending much on application provider's expertise I want to achieve maximum o/p from linux. W.r.t. that I have certain questions as following: How to find out if there is scope for further tcp fine-tuning (without exhausting available resources) as the benchmark values given by vendor looks poor! Is there any parameter value that is available from OS / network stack that will show me the results. If at all there is scope, how shall I identify & configure OS tcp stack parameters i.e. using sysctl or any specific parameter Post tuning how shall I clearly measure performance enhancement / degradation ?

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  • I have to make a simple app that connects devices in a network, but I have no idea of how to this

    - by Gabriel Casado
    I want to write an App for android that has only one ListView. The App will constantly search for anything (mobile devices, desktops, etc.) that is connected in the wifi network. The problem is, I have no idea how to do this. What do I need to study? I comprehend I'd need to use a Thread or a Runnable to constantly search for those devices. Also I know very little about TCP, UDP or any internet protocols. So, can someone give me a basis of what I need to learn to develop this App?

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  • Security review of an authenticated Diffie Hellman variant

    - by mtraut
    EDIT I'm still hoping for some advice on this, i tried to clarify my intentions... When i came upon device pairing in my mobile communication framework i studied a lot of papers on this topic and and also got some input from previous questions here. But, i didn't find a ready to implement protocol solution - so i invented a derivate and as i'm no crypto geek i'm not sure about the security caveats of the final solution: The main questions are Is SHA256 sufficient as a commit function? Is the addition of the shared secret as an authentication info in the commit string safe? What is the overall security of the 1024 bit group DH I assume at most 2^-24 bit probability of succesful MITM attack (because of 24 bit challenge). Is this plausible? What may be the most promising attack (besides ripping the device out off my numb, cold hands) This is the algorithm sketch For first time pairing, a solution proposed in "Key agreement in peer-to-peer wireless networks" (DH-SC) is implemented. I based it on a commitment derived from: A fix "UUID" for the communicating entity/role (128 bit, sent at protocol start, before commitment) The public DH key (192 bit private key, based on the 1024 bit Oakley group) A 24 bit random challenge Commit is computed using SHA256 c = sha256( UUID || DH pub || Chall) Both parties exchange this commitment, open and transfer the plain content of the above values. The 24 bit random is displayed to the user for manual authentication DH session key (128 bytes, see above) is computed When the user opts for persistent pairing, the session key is stored with the remote UUID as a shared secret Next time devices connect, commit is computed by additionally hashing the previous DH session key before the random challenge. For sure it is not transfered when opening. c = sha256( UUID || DH pub || DH sess || Chall) Now the user is not bothered authenticating when the local party can derive the same commitment using his own, stored previous DH session key. After succesful connection the new DH session key becomes the new shared secret. As this does not exactly fit the protocols i found so far (and as such their security proofs), i'd be very interested to get an opinion from some more crypto enabled guys here. BTW. i did read about the "EKE" protocol, but i'm not sure what the extra security level is.

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  • Python - network buffer handling question...

    - by Patrick Moriarty
    Hi, I want to design a game server in python. The game will mostly just be passing small packets filled with ints, strings, and bytes stuffed into one message. As I'm using a different language to write the game, a normal packet would be sent like so: Writebyte(buffer, 5); // Delimit type of message Writestring(buffer, "Hello"); Sendmessage(buffer, socket); As you can see, it writes the bytes to the buffer, and sends the buffer. Is there any way to read something like this in python? I am aware of the struct module, and I've used it to pack things, but I've never used it to actually read something with mixed types stuck into one message. Thanks for the help.

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  • length of captured packets more than MTU

    - by kumar
    Hi, I m running iperf between two machines (linux) and I can observe the mtu of both the interfaces connected is 1500. I ran tcpdump to capture packets and I observed some packets have "length as 2962"....how come this is possible with mtu as only 1500? Please clarify. Thanks! Note: flags field is set as DF. and proto is TCP

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  • How to access a web service behind a NAT?

    - by jr
    We have a product we are deploying to some small businesses. It is basically a RESTful API over SSL using Tomcat. This is installed on the server in the small business and is accessed via an iPhone or other device portable device. So, the devices connecting to the server could come from any number of IP addresses. The problem comes with the installation. When we install this service, it seems to always become a problem when doing port forwarding so the outside world can gain access to tomcat. It seems most time the owner doesn't know router password, etc, etc. I am trying to research other ways we can accomplish this. I've come up with the following and would like to hear other thoughts on the topic. Setup a SSH tunnel from each client office to a central server. Basically the remote devices would connect to that central server on a port and that traffic would be tunneled back to Tomcat in the office. Seems kind of redundant to have SSH and then SSL, but really no other way to accomplish it since end-to-end I need SSL (from device to office). Not sure of performance implications here, but I know it would work. Would need to monitor the tunnel and bring it back up if it goes done, would need to handle SSH key exchanges, etc. Setup uPNP to try and configure the hole for me. Would likely work most of the time, but uPNP isn't guaranteed to be turned on. May be a good next step. Come up with some type of NAT transversal scheme. I'm just not familiar with these and uncertain of how they exactly work. We have access to a centralized server which is required for the authentication if that makes it any easier. What else should I be looking at to get this accomplished?

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  • Matching an IP address with an IP range?

    - by Legend
    I have a MySQL table setup as follows: +---------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+-------------+------+-----+---------+----------------+ | ipaddress_s | varchar(15) | YES | MUL | NULL | | | ipaddress_e | varchar(16) | YES | | NULL | | +---------------+-------------+------+-----+---------+----------------+ where, ipaddress_s and ipaddress_e look something like: 4.100.159.0-4.100.159.255 Now is there a way I can actually get the row that contains a given IP address? For instance, given the IP address: "4.100.159.5", I want the above row to be returned. So I am trying for a query that looks something like this (but of course this is wrong because in the following I am considering IPs as strings): SELECT * FROM ranges WHERE ipaddress_s<"4.100.159.5" AND ipaddress_e>"4.100.159.5" Any suggestions?

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  • Command or tool to display list of connections to a Windows file share

    - by BizTalkMama
    Is there a Windows command or tool that can tell me what users or computers are connected to a Windows fileshare? Here's why I'm looking for this: I've run into issues in the past where our deployment team has deployed BizTalk applications to one of our environments using the wrong bindings, leaving us with two receive locations pointing to the same file share (i.e. both dev and test servers point to dev receive location uri). When this occurs, the two environments in question tend to take turns processing the files received (meaning if I am attempting to debug something in one environment and the other environment has picked the file up, it looks as if my test file has disappeared into thin air). We have several different environments, plus individual developer machines, and I'd rather not have to check each individually to find the culprit. I'm looking for a quick way to detect what locations are connected to the share once I notice my test files vanishing. If I can determine the connections that are invalid, I can go directly to the person responsible for that environment and avoid the time it takes to randomly ask around. Or if the connections appear to be correct, I can go directly to troubleshooting where in the process the message gets lost. Any suggestions?

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  • Discovering maximum packet size

    - by ereOn
    I'm working on a network-related project and I am using DTLS (TLS/UDP) to secure communications. Reading the specifications for DTLS, I've noted that DTLS requires the DF flag (Don't Fragment) to be set. On my local network if I try to send a message bigger than 1500 bytes, nothing is sent. That makes perfect sense. On Windows the sendto() reports a success but nothing is sent. I obviously cannot unset the DF flag manually since it is mandatory for DTLS and i'm not sure whether the 1500 bytes limit (MTU ?) could change in some situations. I guess it can. So, my question is : "Is there a way to discover this limit ?" If not, what would be the lowest possible value ? My software runs under UNIX (Linux/MAC OSX) and Windows OSes so different solutions for each OS are welcome ;) Many thanks.

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  • SQL Latest photos from contacts (grouped by contact)

    - by kitsched
    Hello, To short version of this question is that I want to accomplish something along the lines of what's visible on Flickr's homepage once you're logged in. It shows the three latest photos of each of your friends sorted by date but grouped by friend. Here's a longer explanation: For example I have 3 friends: John, George and Andrea. The list I want to extract should look like this: George Photo - 2010-05-18 Photo - 2010-05-18 Photo - 2010-05-12 John Photo - 2010-05-17 Photo - 2010-05-14 Photo - 2010-05-12 Andrea Photo - 2010-05-15 Photo - 2010-05-15 Photo - 2010-05-15 Friend with most recent photo uploaded is on top but his or her 2 next files follow. I'd like to do this from MySQL, and for the time being I got here: SELECT photos.user_id, photos.id, photos.date_uploaded FROM photos WHERE photos.user_id IN (SELECT user2_id FROM user_relations WHERE user1_id = 8) ORDER BY date_uploaded DESC Where user1_id = 8 is the currently logged in user and user2_id are the ids of friends. This query indeed returns the latest files uploaded by the contacts of the user with id = 8 sorted by date. However I'd like to accomplish the grouping and limiting mentioned above. Hopefully this makes sense. Thank you in advance.

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  • S3 file Uploading from Mac app though PHP?

    - by Ilija Tovilo
    I have asked this question before, but it was deleted due too little information. I'll try to be more concrete this time. I have an Objective-C mac application, which should allow users to upload files to S3-storage. The s3 storage is mine, the users don't have an Amazon account. Until now, the files were uploaded directly to the amazon servers. After thinking some more about it, it wasn't really a great concept, regarding security and flexibility. I want to add a server in between. The user should authenticate with my server, the server would open a session if the authentication was successful, and the file-sharing could begin. Now my question. I want to upload the files to S3. One option would be to make a POST-request and wait until the server would receive the file. Problems here are, that there would be a delay, when the file is being uploaded from my server to the S3 servers, and it would double the uploading time. Best would be, if I could validate the request, and then redirecting it, so the client uploads it directly to the s3-storage. Not sure if this is possible somehow. Uploading directly to S3 doesn't seem to be very smart. After looking into other apps like Droplr and Dropmark, it looks like they don't do this. Btw. I did this using Little Snitch. They have their api on their own web-server, and that's it. Could someone clear things up for me? EDIT How should I transmit my files to S3? Is there a way to "forward" it, or do I have to upload it to my server and then upload it from there to S3? Like I said, other apps can do this efficiently and without the need of communicating with S3 directly.

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