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  • [java] reading POST data from html form sent to serversocket.

    - by user32167
    i try to write simplest possible server app in Java, displaying html form with textarea input, which after submitting gives me possibility to parse xml typed in thet textarea. For now i build simple serversocket based server like that: import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; public class WebServer { protected void start() { ServerSocket s; String gets = ""; System.out.println("Start on port 80"); try { // create the main server socket s = new ServerSocket(80); } catch (Exception e) { System.out.println("Error: " + e); return; } System.out.println("Waiting for connection"); for (;;) { try { // wait for a connection Socket remote = s.accept(); // remote is now the connected socket System.out.println("Connection, sending data."); BufferedReader in = new BufferedReader(new InputStreamReader( remote.getInputStream())); PrintWriter out = new PrintWriter(remote.getOutputStream()); String str = "."; while (!str.equals("")) { str = in.readLine(); if (str.contains("GET")){ gets = str; break; } } out.println("HTTP/1.0 200 OK"); out.println("Content-Type: text/html"); out.println(""); // Send the HTML page String method = "get"; out.print("<html><form method="+method+">"); out.print("<textarea name=we></textarea></br>"); out.print("<input type=text name=a><input type=submit></form></html>"); out.println(gets); out.flush(); remote.close(); } catch (Exception e) { System.out.println("Error: " + e); } } } public static void main(String args[]) { WebServer ws = new WebServer(); ws.start(); } } After form (textarea with xml and one additional text input) is submitted in 'gets' String-type variable I have Urlencoded values of my variables (also displayed on the screen, it looks like that: gets = GET /?we=%3Cnetwork+ip_addr%3D%2210.0.0.0%2F8%22+save_ip%3D%22true%22%3E%0D%0A%3Csubnet+interf_used%3D%22200%22+name%3D%22lan1%22+%2F%3E%0D%0A%3Csubnet+interf_used%3D%22254%22+name%3D%22lan2%22+%2F%3E%0D%0A%3C%2Fnetwork%3E&a=fooBar HTTP/1.1 What can i do to change GET to POST method (if i simply change it in form and than put " if (str.contains("GET")){" it gives me string like gets = POST / HTTP/1.1 with no variables. And after that, how i can use xml from my textarea field (called 'we')?

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  • First time using select(), maybe a basic question?

    - by darkletter
    Hello people, i've been working for a few days with this server using select(). What it does, is that, i have two arrays of clients (one is "suppliers", and the other is "consumers"), and the mission of the server is to check whether the suppliers have something to send to the consumers, and in case affirmative, send it. The second part of the server is that, when the consumers have received the suppliers' info, they send a confirmation message to the same suppliers that sent the info. When a client connects, it gets recognized as "undefined", until it sends a message with the word "supplier" or "consumer" (in Spanish, as i'm from there), when the server puts it in the correct clients array. Well, what the server does is not very important here. What's important is that, i'm doing both parts with two different "for" loops, and that's where i'm getting the problems. When the first user connects to the server (be it a supplier or a consumer), the server gets stuck in the first or second loop, instead of just continuing its execution. As it's the first time i'm using select(), i may be missing something. Could you guys give me any sort of help? Thanks a lot in advance. for(;;) { rset=allset; nready=select(maxfd+1,&rset,NULL,NULL,NULL); if (FD_ISSET(sockfd, &rset)){ clilen=sizeof(cliente); if((connfd=accept(sockfd,(struct sockaddr *)&cliente,&clilen))<0) printf("Error"); IP=inet_ntoa(cliente.sin_addr); for(i=0;i<COLA;i++){if(indef[i]<0){indef[i]=connfd;IPind[i]=IP;break;}} FD_SET(connfd,&allset); if(connfd > maxfd) maxfd=connfd; if(i>maxii) maxii=i; if(--nready<=0) continue; }// Fin ISSET(sockfd) for(i=0;i<=maxii;i++){ if((sockfd1=indef[i])<0){ continue;} //! if(FD_ISSET(sockfd1,&rset)){ if((n=read(sockfd1,comp,MAXLINE))==0){close(sockfd1);FD_CLR(sockfd1,&allset);indef[i]=-1;printf("Cliente indefinido desconectado \n");} else{ comp[n]='\0'; if(strcmp(comp,"suministrador")==0){ for(j=0;j<=limite;j++){if(sumi[j]<0){IPsum[j]=IPind[i];sumi[j]=indef[i]; indef[i]=-1;if(j>maxis) {maxis=j;}break; } } } else if(strcmp(comp,"consumidor")==0){ for(o=0;j<=limite;j++){if(consum[o]<0){IPcons[o]=IPind[i];consum[o]=indef[i]; indef[o]=-1;if(o>maxic) {maxic=o;}break; } } } if(--nready <=0)break; } } }//fin bucle for maxii for(i=0;i<=maxis;i++){ if((sockfd2=sumi[i])<0){continue;} if(FD_ISSET(sockfd2,&rset)){ if((n=read(sockfd2,buffer2,MAXLINE))==0){close(sockfd2);FD_CLR(sockfd2,&allset);sumi[i]=-1;printf("Suministrador desconectado \n");} else{ buffer2[n]='\0'; for(j=0;j<=maxic;j++){ if((sockfd3=consum[j])<0){ continue;} else {strcpy(final,IPsum[i]);strcat(final,":");strcat(final,buffer2);write(sockfd3,final,sizeof(final));respuesta[i]=1;} } break; // ? } } }//fin for maxis for(i=miniic;i<=maxic;i++){ if((sockfd4=consum[i])<0){continue;} if(FD_ISSET(sockfd4,&rset)){ if((n=read(sockfd4,buffer3,MAXLINE))==0){close(sockfd4);FD_CLR(sockfd4,&allset);consum[i]=-1;printf("Consumidor desconectado \n");} else{ buffer3[n]='\0'; IP2=strtok(buffer3,":"); obj=strtok(NULL,":"); for(j=0;j<100;j++){ if((strcmp(IPsum[j],IP2)==0) && (respuesta[j]==1)) {write(sumi[j],obj,sizeof(obj)); miniic=i+1; respuesta[j]=0; break; } } } } }

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  • Why use an event cache with epoll_wait?

    - by user1827356
    Question: epoll man page has some pointers when using epoll with an 'event cache'. But, why would you need to maintain an event cahce at all - Isn't this the same as what epoll is supposed to be doing? Is it to avoid making multiple epoll_wait calls which might be slower than managing the events in user space? Is it to implement a custom 'priority' scheme over the cached events? Background: I'm trying to understand the strengths/shortcomings of epoll and its applicability to different situations

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  • Waiting for data via select not working

    - by BSchlinker
    I'm currently working on a project which involves multiple clients connected to a server and waiting for data. I'm using select and monitoring the connection for incoming data. However, the client just continues to print nothing, acting as if select has discovered incoming data. Perhaps I'm attacking this wrong? For the first piece of data the server does send, it is displayed correctly. However, the server then disconnects and the client continues to spew blank lines. FD_ZERO(&readnet); FD_SET(sockfd, &readnet); while(1){ rv = select(socketdescrip, &readnet, NULL, NULL, &timeout); if (rv == -1) { perror("select"); // error occurred in select() } else if (rv == 0) { printf("Connection timeout! No data after 10 seconds.\n"); } else { // one or both of the descriptors have data if (FD_ISSET(sockfd, &readnet)) { numbytes = recv(sockfd, buf, sizeof buf, 0); printf("Data Received\n"); buf[numbytes] = '\0'; printf("client: received '%s'\n",buf); sleep(10); } } }

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  • Concurrent connections in C# socket

    - by Chu Mai
    There are three apps run at the same time, 2 clients and 1 server. The whole system should function as following: The client sends an serialized object to server then server receives that object as a stream, finally the another client get that stream from server and deserialize it. This is the sender: TcpClient tcpClient = new TcpClient(); tcpClient.Connect("127.0.0.1", 8888); Stream stream = tcpClient.GetStream(); BinaryFormatter binaryFormatter = new BinaryFormatter(); binaryFormatter.Serialize(stream, event); // Event is the sending object tcpClient.Close(); Server code: TcpListener listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 8888); listener.Start(); Console.WriteLine("Server is running at localhost port 8888 "); while (true) { Socket socket = listener.AcceptSocket(); try { Stream stream = new NetworkStream(socket); // Typically there should be something to write the stream // But I don't knwo exactly what should the stream write } catch (Exception e) { Console.WriteLine("Exception: " + e.Message); Console.WriteLine("Disconnected: {0}", socket.RemoteEndPoint); } } The receiver: TcpClient client = new TcpClient(); // Connect the client to the localhost with port 8888 client.Connect("127.0.0.1", 8888); Stream stream = client.GetStream(); Console.WriteLine(stream); when I run only the sender and server, and check the server, server receives correctly the data. The problem is when I run the receiver, everything is just disconnected. So where is my problem ? Could anyone point me out ? Thanks

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  • Use of select or multithread for almost 80 or more clients?

    - by Tushar Goel
    I am working on one project in which i need to read from 80 or more clients and then write their o/p into a file continuously and then read these new data for another task. My question is what should i use select or multithreading? Also I tried to use multi threading using read/fgets and write/fputs call but as they are blocking calls and one operation can be performed at one time so it is not feasible. Any idea is much appreciated. update 1: I have tried to implement the same using condition variable. I able to achieve this but it is writing and reading one at a time.When another client tried to write then it cannot able to write unless i quit from the 1st thread. I do not understand this. This should work now. What mistake i am doing? Update 2: Thanks all .. I am able to succeeded to get this model implemented using mutex condition variable. updated Code is as below: **header file******* char *mailbox ; pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER ; pthread_cond_t writer = PTHREAD_COND_INITIALIZER; int main(int argc,char *argv[]) { pthread_t t1 , t2; pthread_attr_t attr; int fd, sock , *newfd; struct sockaddr_in cliaddr; socklen_t clilen; void *read_file(); void *update_file(); //making a server socket if((fd=make_server(atoi(argv[1])))==-1) oops("Unable to make server",1) //detaching threads pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED); ///opening thread for reading pthread_create(&t2,&attr,read_file,NULL); while(1) { clilen = sizeof(cliaddr); //accepting request sock=accept(fd,(struct sockaddr *)&cliaddr,&clilen); //error comparison against failire of request and INT if(sock==-1 && errno != EINTR) oops("accept",2) else if ( sock ==-1 && errno == EINTR) oops("Pressed INT",3) newfd = (int *)malloc(sizeof(int)); *newfd = sock; //creating thread per request pthread_create(&t1,&attr,update_file,(void *)newfd); } free(newfd); return 0; } void *read_file(void *m) { pthread_mutex_lock(&lock); while(1) { printf("Waiting for lock.\n"); pthread_cond_wait(&writer,&lock); printf("I am reading here.\n"); printf("%s",mailbox); mailbox = NULL ; pthread_cond_signal(&writer); } } void *update_file(int *m) { int sock = *m; int fs ; int nread; char buffer[BUFSIZ] ; if((fs=open("database.txt",O_RDWR))==-1) oops("Unable to open file",4) while(1) { pthread_mutex_lock(&lock); write(1,"Waiting to get writer lock.\n",29); if(mailbox != NULL) pthread_cond_wait(&writer,&lock); lseek(fs,0,SEEK_END); printf("Reading from socket.\n"); nread=read(sock,buffer,BUFSIZ); printf("Writing in file.\n"); write(fs,buffer,nread); mailbox = buffer ; pthread_cond_signal(&writer); pthread_mutex_unlock(&lock); } close(fs); }

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  • Strange numbers in java socket output

    - by user293163
    I have small test app: Socket socket = new Socket("jeck.ru", 80); PrintWriter pw = new PrintWriter(socket.getOutputStream(), false); pw.println("GET /ip/ HTTP/1.1"); pw.println("Host: jeck.ru"); pw.println(); pw.flush(); BufferedReader rd = new BufferedReader(new InputStreamReader(socket.getInputStream())); String str; while ((str = rd.readLine()) != null) { System.out.println(str); } It`s output: HTTP/1.1 200 OK Date: Sat, 13 Mar 2010 22:06:51 GMT Content-Type: text/html;charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive Keep-Alive: timeout=5 Server HTTP/1.1 200 OK Date: Sat, 13 Mar 2010 22:06:51 GMT Content-Type: text/html;charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive Keep-Alive: timeout=5 Server: Apache Cache-Control: max-age=0 Expires: Sat, 13 Mar 2010 22:06:51 GMT 123 <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>??? IP</title> </head> <body> <div style='text-align: center; font: 32pt Verdana;margin-top: 300px'> ??? IP &#151; 94.103.87.153 </div> </body> </html> 0 Whence these numbers (123 an 0) takes?

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  • Why can't a bind linux service to the loop-back only?

    - by Jon Trauntvein
    I am writing a server application that will provide a service on an ephemeral port that I only want accessible on the loopback interface. In order to do this, I am writing code like the following: struct sockaddr_in bind_addr; memset(&bind_addr,0,sizeof(bind_addr)); bind_addr.sin_family = AF_INET; bind_addr.sin_port = 0; bind_addr.sin_addr.s_addr = htonl(inet_addr("127.0.0.1")); rcd = ::bind( socket_handle, reinterpret_cast<struct sockaddr *>(&bind_addr), sizeof(bind_addr)); The return value for this call to bind() is -1 and the value of errno is 99 (Cannot assign requested address). Is this failing because inet_addr() already returns its result in network order or is there some other reason?

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  • Interview Questions that can be asked on TCP/IP, UDP, Socket Programming ?

    - by Shantanu Gupta
    I am going for an interview day after tomorrow where i will be asked vaious questions related to TCP/IP and UDP. As of now i have prepared theoritical knowledge about it. But now I am looking up for gaining some practicle knowledge related to how it works in a network. What all is going in vaious .NET classes. I want to create a very small application like a chat or something that can make me all these concepts very much clear. Could you please suggest some questions related to TCP/IP that you generally ask or that you might have faced. How communication is going from server to client. Right now I am studying TcpClient, TcpListener and UdpClient Class but I want to implement all of them so as to get aware about its working. Is Chat application a Tcp/IP application ? I would appreciate your help.

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  • What happens to an instance of ServerSocket blocked inside accept(), when I drop all references to i

    - by Hanno Fietz
    In a multithreaded Java application, I just tracked down a strange-looking bug, realizing that what seemed to be happening was this: one of my objects was storing a reference to an instance of ServerSocket on startup, one thread would, in its main loop in run(), call accept() on the socket while the socket was still waiting for a connection, another thread would try to restart the component under some conditions, the restart process missed the cleanup sequence before it reached the initialization sequence as a result, the reference to the socket was overwritten with a new instance, which then wasn't able to bind() anymore the socket which was blocking inside the accept() wasn't accessible anymore, leaving a complete shutdown and restart of the application as the only way to get rid of it. Which leaves me wondering: with no references left to the ServerSocket instance, what would free the socket for a new connection? At what point would the ServerSocket become garbage collected? In general, what are good practices I can follow to avoid this type of bug?

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  • Reason for socket.error

    - by August Flanagan
    Hi, I am a complete newbie when it comes to python, and programming in general. I've been working on a little webapp for the past few weeks trying to improve my coding chops. A few days ago my laptop was stolen so I went out and got a new MacBook Pro. Thank God I had everything under subversion control. The problem is now that I am on my new machine a script that I was running has stopped working and I have no idea why. This is really the only part of what I have been writing that I borrowed heavily for existing scripts. It is from the widely available whois.py script and I have only slightly modified it as follows (see below). It was running fine on my old system (running ubuntu), but now the socket.error is being raised. I'm completely lost on this, and would really appreciate any help. Thanks! def is_available(domainname, whoisserver="whois.verisign-grs.com", cache=0): if whoisserver is None: whoisserver = "whois.networksolutions.com" s = None while s == None: try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setblocking(0) try: s.connect((whoisserver, 43)) except socket.error, (ecode, reason): if ecode in (115, 150): pass else: raise socket.error, (ecode, reason) ret = select.select([s], [s], [], 30) if len(ret[1])== 0 and len(ret[0]) == 0: s.close() raise TimedOut, "on connect " s.setblocking(1) except socket.error, (ecode, reason): print ecode, reason time.sleep(1) s = None s.send("%s \n\n" % domainname) page = "" while 1: data = s.recv(8196) if not data: break page = page + data s.close()

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  • python send/receive hex data via TCP socket

    - by Mike
    I have a ethenet access control device that is said to be able to communicate via TCP. How can i send a pachet by entering the HEX data, since this is what i have from their manual (a standard format for the communication packets sent and received after each command)

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  • A non-blocking server with java.io

    - by Jon
    Everybody knows that java IO is blocking, and java NIO is non-blocking. In IO you will have to use the thread per client pattern, in NIO you can use one thread for all clients. Now my question follows: is it possible to make a non-blocking design using only the Java IO api. (not NIO) I was thinking about a pattern like this (obviously very simplified); List<Socket> li; for (Socket s : li) { InputStream in = s.getInputStream(); byte[] data = in.available(); in.read(data); // processData(data); (decoding packets, encoding outgoing packets } Also note that the client will always be ready for reading data. What are your opinions on this? Will this be suitable for a server that should at least hold a few hundred of clients without major performance issues?

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  • How can I forcibly close a TcpListener

    - by Nissim
    I have a service which communicates through tcpListener. Problem is when the user restarts the service - an "Address already in use" exception is thrown, and the service cannot be started for a couple of minutes or so. Is there's any way of telling the system to terminate the old connection so I can open a new one? (I can't just use random ports because there is no way for the service to notify the clients what is the port, so we must depend on a predefined port)

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  • Reading TCP Sequence Number Before Sending a Packet

    - by Sadeq Dousti
    I'm writing a C/C++ client-server program under Linux. Assume a message m is to be sent from the client to the server. Is it possible for the client to read the TCP sequence number of the packet which will carry m, before sending m? In fact, I'd like to append this sequence number to m, and send the resulting packet. (Well, things are more complicated, but let's keep it that simple. In fact, I'd like to apply authentication info to this sequence number, and then append it to m.) Moreover, is it possible for the server to read the TCP sequence number of the packet carrying m?

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  • udp server unable to transmit data

    - by mawia
    Hi! all, I have written a simple udp server which has to transmit certain data to few of it's clients. but though server is successfully executing send,but unable to transmit even a single byte.The return value of send is 0 although I have enough data to be transmitted.you can see the code for the said server here: http://pastebin.com/zeMcwd6X Can you people help in finding the possible culprit for the same.Any reply in this regard will be appreciated. Lot of Thanks in advance! Mawia

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  • Hold a network connection although IP address change

    - by rursw1
    Hi, Is it possible to hold an open TCP connection with a client, while the IP address of the client is externally changed? For example, the connection is establishes against address X, but somewhen while the connection is open, the client-side user asks for IP renew and gets another IP address. Can the connection remains alive in this case? Thanks in advance.

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  • Receive input over TCP/IP and use it to update HTML

    - by mawg
    This has got to be a FAQ, so can someone please just direct me to a "network programming for dummies" URL? The server wants to push information to a client or broadcast to all, when an event happens - as opposed to the clients constantly polling the server "just in case". The client then updates a browser page display. How do I do that? (toldya it was a n00b question) Should I have a thread which receives info on a socket and then writes it to a database which the browser display (PHP) can process with an HTML refresh tag, or what? Sorry to sound so dumb.

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  • trying to WHOIS a site within IRC

    - by SourD
    if data.find('!whois') != -1: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(("com.whois-servers.net", 43)) s.send('www.msn.com' + "\r\n") response = '' while True: d = s.recv(4096) response += d if d == '': break s.send('PRIVMSG ' + chan + " " + response + '\r\n') s.close() when I type !whois on the channel, it doesnt do anything, I'm probably doing this wrong. Any help will be appreciate it. Thanks. Note: There's another socket already connected.

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  • Socket Programming for the Web

    - by Benny
    I have to interact with a legacy system that accepts socket communication and messages. My goal is to make the application cross-platform, but I need the ability to push messages to the client (i.e. - .NET's WCF, Java's Comet) and detect when the user closes out of their browser to destroy the socket. I have built a prototype of .NET wrapper + WCF + Silverlight but it is so disconnected it is difficult to manage the state of the user and seems to be a nightmare to support. All of that considered, what would be my best option?

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  • What is wrong with this Asynchronus task?

    - by bluebrain
    the method onPostExecute simply was not executed, I have seen 16 at LogCat but I can not see 16 in LogCAT. I tried to debug it, it seemed that it goes to the first line of the class (package line) after return statement. private class Client extends AsyncTask<Integer, Void, Integer> { protected Integer doInBackground(Integer... params) { Log.e(TAG,10+""); try { socket = new Socket(target, port); Log.e(TAG,11+""); oos = new ObjectOutputStream(socket.getOutputStream()); Log.e(TAG,14+""); ois = new ObjectInputStream(socket.getInputStream()); Log.e(TAG,15+""); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } Log.e(TAG,16+""); return 1; } protected void onPostExecute(Integer result) { Log.e(TAG,13+""); try { Log.e(TAG,12+""); oos.writeUTF(key); Log.e(TAG,13+""); if (ois.readInt() == OKAY) { isConnected = true; Log.e(TAG,14+""); }else{ Log.e(TAG,15+""); isConnected = false; } } catch (IOException e) { e.printStackTrace(); isClosed = true; } } }

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  • Java blocking socket returning incomplete ByteBuffer

    - by evandro-carrenho
    I have a socketChannel configured as blocking, but when reading byte buffers of 5K from this socket, I get an incomplete buffer sometimes. ByteBuffer messageBody = ByteBuffer.allocate(5*1024); messageBody.mark(); messageBody.order(ByteOrder.BIG_ENDIAN); int msgByteCount = channel.read(messageBody); Ocasionally, messageBody is not completely filled and channel.read() does not return -1 or an exception, but the actual number of bytes read (which is less than 5k). Has anyone experienced a similar problem?

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