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  • how to create multiple tcp connections between server and client

    - by lowcosthighperformance
    I am new in Unix/Linux networking programming, so I have written server-client program in below.In this code there is one socket between client and server, client requests to server, then server responses from 1 to 100 numbers to client. So my question is how can we do this process with 3 socket( tcp connection) without using thread? ( e.g. First socket runs then second runs then third runs then first again .. ) Do you have any suggestion? Thank you client.c int main() { int sock; struct sockaddr_in sa; int ret; char buf[1024]; int x; sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_port = htons(SERVER_PORT); inet_pton (AF_INET, SERVER_IP, &sa.sin_addr); ret = connect (sock, (const struct sockaddr *) &sa,sizeof (sa)); if (ret != 0) { printf ("connect failed\n"); exit (0); } x = 0; while (x != -1) { read (sock, buf , sizeof(int)); x = ntohl(*((int *)buf)); if (x != -1) printf ("int rcvd = %d\n", x); } close (sock); exit (0); } server.c int main() { int list_sock; int conn_sock; struct sockaddr_in sa, ca; socklen_t ca_len; char buf[1024]; int i; char ipaddrstr[IPSTRLEN]; list_sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_addr.s_addr = htonl(INADDR_ANY); sa.sin_port = htons(SERVER_PORT); bind (list_sock,(struct sockaddr *) &sa,sizeof(sa)); listen (list_sock, 5); while (1){ bzero (&ca, sizeof(ca)); ca_len = sizeof(ca); // important to initialize conn_sock = accept (list_sock,(struct sockaddr *) &ca,&ca_len); printf ("connection from: ip=%s port=%d \n",inet_ntop(AF_INET, &(ca.sin_addr), ipaddrstr, IPSTRLEN),ntohs(ca.sin_port)); for (i=0; i<100; ++i){ *((int *)buf) = htonl(i+20); // we using converting to network byte order write (conn_sock, buf, sizeof(int)); } * ((int *)buf) = htonl(-1); write (conn_sock, buf, sizeof(int)); close (conn_sock); printf ("server closed connection to client\n"); } }

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  • Maintaining many socket connections with a single thread

    - by John
    Many tutorials on socket communication I see seem to use 1 thread per socket. But on a server used for online gaming, you might have 10k concurrent users - 10k threads isn't probably a wonderful idea. I came across a tool (SmartFox) which claims to use a single thread for monitoring all socket connections, potentially thousands of them. This app happens to be in Java, but I figure C++ or C# could do the same... how would you achieve this?

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  • Weird send() problem (with Wireshark log)

    - by Meta
    I had another question about this issue, but I didn't ask properly, so here I go again! I'm sending a file by sending it in chunks. Right now, I'm playing around with different numbers for the size of that chunk, to see what size is the most efficient. When testing on the localhost, any chunk size seems to work fine. But when I tested it over the network, it seems like the maximum chunk size is 8191 bytes. If I try anything higher, the transfer becomes extremely, painfully, slow. To show what happens, here are the first 100 lines of Wireshark logs when I use a chunk size of 8191 bytes, and when I use a chunk size of 8192 bytes: (the sender is 192.168.0.102, and the receiver is 192.168.0.100) 8191: http://pastebin.com/E7jFFY4p 8192: http://pastebin.com/9P2rYa1p Notice how in the 8192 log, on line 33, the receiver takes a long time to ACK the data. This happens again on line 103 and line 132. I believe this delay is the root of the problem. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. So my question is, why am I getting delayed ACKs when sending files in chunks of 8192 bytes, when everything works fine when using chunks of 8191 bytes? Edit: As an experiment, I tried to do the file transfer in the other direction (from 192.168.0.100 to 192.168.0.102), and surprisingly, any number worked! (Although numbers around 8000 seemed to perform the smoothest). So then the problem is with my computer! But I'm really not sure what to check for. Edit 2: Here is the pseudocode I use to send and receive data.

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  • Keeping socket open to send files on timer calls?

    - by user3704768
    I'm writing a program that requires an image to be fetched from a remote server every 10 milliseconds or so, as that's how often the image is updated. My current method calls a timer to grab the image, but it encounters Socket Closed errors all the time, and sometimes does not work at all. How can I fix my methods to keep the socket open the whole time, so no reconnecting is needed? Here is the full class: import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.net.InetAddress; import java.net.InetSocketAddress; import java.net.ServerSocket; import java.net.Socket; import java.net.UnknownHostException; import javax.swing.Timer; public class Connection { public static void createServer() throws IOException { Capture.getScreen(); ServerSocket socket = null; try { socket = new ServerSocket(12345, 0, InetAddress.getByName("127.0.0.1")); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } System.out.println("Server started on " + socket.getInetAddress().getHostAddress() + ":" + socket.getLocalPort() + ",\nWaiting for client to connect."); final Socket clientConnection = socket.accept(); System.out.println("Client accepted from " + clientConnection.getInetAddress().getHostAddress() + ", sending file"); ActionListener taskPerformer = new ActionListener() { public void actionPerformed(ActionEvent evt) { System.out.println("Sending File"); try { pipeStreams(new FileInputStream(new File( "captures/sCap.png")), clientConnection.getOutputStream(), 1024); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }; System.out.println("closing out connection"); try { clientConnection.close(); } catch (IOException e) { e.printStackTrace(); } try { socket.close(); } catch (IOException e) { e.printStackTrace(); } Timer timer = new Timer(10, taskPerformer); timer.setRepeats(true); timer.start(); } public static void createClient() throws IOException { System.out.println("Connecting to server."); final Socket socket = new Socket(); try { socket.connect(new InetSocketAddress(InetAddress .getByName("127.0.0.1"), 12345)); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { } ActionListener taskPerformer = new ActionListener() { public void actionPerformed(ActionEvent evt) { System.out.println("Success, retreiving file."); try { pipeStreams(socket.getInputStream(), new FileOutputStream( new File("captures/rCap.png")), 1024); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { } } }; System.out.println("Closing connection"); try { socket.close(); } catch (IOException e) { e.printStackTrace(); } Timer timer = new Timer(10, taskPerformer); timer.setRepeats(true); timer.start(); } public static void pipeStreams(java.io.InputStream source, java.io.OutputStream destination, int bufferSize) throws IOException { byte[] buffer = new byte[bufferSize]; int read = 0; while ((read = source.read(buffer)) != -1) { destination.write(buffer, 0, read); } destination.flush(); destination.close(); source.close(); } }

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  • Why my java app for android not connect to server?

    - by FredVaz
    Why my java app for android not connect to server ? I run the aplication in android emulator, and the server wich port 9999 and host 127.0.0.1 in my pc, but just not connect and i think this method isn't good for android app. It is my source code: import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; //Java imports //import android.util.Log; import java.io.*; import java.net.*; import java.util.*; import java.util.logging.Level; import java.util.logging.Logger; public class MainActivity extends Activity { //Variaveis Interface private Button ligar; private Button enviar; private EditText text1; private TextView text2; //Variaveis static Socket cSocket; static PrintWriter out; static BufferedReader in; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //Declaração butões ligar = (Button) findViewById(R.id.ligar); enviar = (Button) findViewById(R.id.enviar); text1 = (EditText) findViewById(R.id.text1); text2 = (TextView) findViewById(R.id.text2); //Interacao ligar.setOnClickListener(new OnClickListener(){ public void onClick(View arg0){ connect(); } }); enviar.setOnClickListener(new OnClickListener(){ public void onClick(View arg0){ out.println("Hello"); text2.setText(""); } }); } //Outras Funcoes public void connect(){ //Funcao ligar cSocket = null; out = null; in = null; try { cSocket = new Socket("127.0.0.1",9999); out = new PrintWriter(cSocket.getOutputStream(), true); in = new BufferedReader(new InputStreamReader(cSocket.getInputStream())); text2.setText("Estas conectado com sucesso."); } catch (IOException ex) { //Logger.getLogger(client.class.getName()).log(Level.SEVERE, null, ex); text2.setText("Erro! Na conexão"); } } // }

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  • Running Java Server Application 24/7 (NOT on local machine) ...?

    - by Steven
    I am currently experimenting with Java Socket Programming and succeeded in creating a simple application that allows me to send data back and forth between a client and a server. I don't want to power my laptop (on which the server application runs) 24/7. Therefore, of course, no computer (that runs my client application) will be able to communicate with my selfmade server application as long as my laptop is turned off. Now I'd like to know: (1) Is it possible to run the server application on a remote (physical) server, so that I don't need my laptop for that purpose? (2) If yes, do you have any suggestions where I could rent such a remote server? As I said, I'm just curious about how all that stuff works. I don't really something expensive.

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  • How to approach socket programming between C# -> Java (Android)

    - by Alex
    I've recently knocked up a server/client app for Windows & Android that allows one to send a file from Windows to an android phone over a socket connection. It works great for a single file but trying to send multiple files over in a single stream is causing me problems. I've also realised that aside from the binary data, I will need to send messages over the socket to indicate error states and other application messages. I have little experience with network programming and and wondering what is the best way forward. Basically the C# server side of the app just goes into a listening state and uses Socket.SendFile to transmit the file. On Android I use the standard Java Socket.getInputStream() to receive the file. That works great for a single file transfer, but how should I handle multiple files and error/messaging information? Do I need to use a different socket for each file? Should I be using a higher level framework to handle this or can I send everything over the single socket? Any other suggestions for frameworks or learning materials?

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  • How to break a loop when inputting unspecified raw_input?

    - by user1874510
    I want to write an interface using a while loop and raw_input. My code looks like this: while True: n = raw_input("'p' = pause, 'u' = unpause, 'p' = play 's' = stop, 'q' = quit) if n.strip() == 'p': mp3.pause() if n.strip() == 'u': mp3.unpause() if n.strip() == 'p': mp3.play() if n.strip() == 's': mp3.stop() if n.strip() == 'q': break But I want it to break if I input anything that isn't specified in the raw_input. if not raw_input: break Returns and IndentationError: unindent does not match any outer indentation level. if not raw_input: break Does not return any error but doesn't work as I want it to. As far as I know, it does nothing at all. Also, if there's a cleaner way to write my loop, I love to hear it.

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  • How to avoid my script to freeze

    - by jemz
    I have socket server script that continuously running listening for the GPS device that runs in PHP CLI,my problem is that my socket will freeze if it executes long time,how do I prevent this so that my script will not freeze.I have no idea on this socket.this is the first time that I use socket connection. I appreciate someone can help my problem. <?php error_reporting(-1); ini_set('display_errors', 1); set_time_limit (0); $address_server = 'xxx.xxx.xx.xx'; $port_server = xxxx; $isTrue = true; socketfunction($address_server,$port_server,$isTrue); function socketfunction($address,$port,$done){ $sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1); socket_bind($sock, $address, $port); socket_listen($sock); $clients = array($sock); while ($done ) { $file = fopen('txt.log','a'); $read = $clients; $write = NULL; $except = NULL; $tv_sec = 0; if (socket_select($read, $write , $except, $tv_sec) < 1){ continue; } // checking client if (in_array($sock, $read)) { $clients[] = $newsock = socket_accept($sock); $key = array_search($sock, $read); unset($read[$key]); } //handle client for reading foreach ($read as $read_sock) { $data = @socket_read($read_sock, 1024, PHP_NORMAL_READ); if ($data === false) { $key = array_search($read_sock, $clients); unset($clients[$key]); echo "client disconnected.\n"; echo "Remaining ".(count($clients) - 1)."client(s) connected\r\n"; continue; } $data = trim($data); if (!empty($data)) { echo("Returning stripped input\n"); fwrite($file,$data."\n"); } } // end of reading foreach fclose($file); }//end while socket_close($sock); } ?> Thank you in advance.

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  • C# equivalent of recv?

    - by mlh
    Hello, I have a portion of C code that I am trying to port over to C#. In my C code, I create a socket and then issue a receive command. The receive command is void receive(mysocket, char * command_buffer) { recv(mysocket, command_buffer, COMMAND_BUFFER_SIZE, 0); } now, the command buffer is returned with new values including command_buffer[8] being a pointer to a string. I'm really confused as to how to do this in C# because C# Read() command specifically takes in bytes and not char. The important part is that I get the pointer to the string. Any ideas?

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  • Read from socket

    - by Alberto
    I need to read from an AF_UNIX socket to a buffer using the function read from C, but I don't know the buffer size. I think the best way is to read N bytes until the read returns 0 (no more writers in the socket). Is this correct? Is there a way to guess the size of the buffer being written on the socket? I was thinking that a socket is a special file. Opening the file in binary mode and getting the size would help me in knowing the correct size to give to the buffer? I'm a very new to C, so please keep that in mind.

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  • linux process scheduling delayed for long time

    - by Medicine
    I have done strace on my multi-threaded c++ application running on linux after couple hours of running, none of the threads got run, for about 12 seconds. I have seen that the unfinished select system call which is called with a timeout was unfinished before the thread was suspended, reported after it resumed that, it took 11.x seconds for the operation to finish. This is clear indication that the process got starved for a long time. All threads in the process are created with default scheduling policy(SCHED_OTHER) of linux and default priority. There are another 5 similar apps running on the same box which are also heavy I/O bound like this app due to heavy data received on the socket. But most of the time, this app is getting scheduled delay. The other apps are created with same sched policy and priority as this i.e. the defaults. why is only this process gets blocked almost all of the time? Could it be because this process is more I/O intensive as in more busy due to may be higher rates of data? So, the linux dynamic priority adjusting in play here which pushed this process down?

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  • Sending compres data via socket

    - by Pizza
    Hi, I have to make a log server in java, and one task is to send the data compressed. Now I am sending it line by line in plain text, but I must compress it. The server handle "HTTP like" request. For example, I can get a log sending "GET xxx.log". This will entablish a TCP connection to the server, the server response with a header and the log, and close the connection. The client, reads line by line and analyzes each LOG entry. I tried some ways without success. My main problem is that I don't know where each line ends(in the client size). Any idea?

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  • WinSock best accept() practices

    - by Meta
    Imagine you have a server which can handle only one client at a time. The server uses WSAAsyncSelect to be notified of new connections. In this case, what is the best way of handling FD_ACCEPT messages: A Accept the connection attempt right away but queue the client until its turn? B Do not accept the next connection attempt until we are done serving the currently connected client? What do you guys think is the most efficient?

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  • c# How to get string from byte?

    - by Kade
    I have a form-console application which does a TCP socket connections for send and receive. I need help getting the following response to STRING. The following code does write the RESPONSE to the console, but i also want to byte[] b = new byte[100]; int k = s.Receive(b); Console.WriteLine("Recieved..."); for (int i = 0; i < k; i++) Console.Write(Convert.ToChar(b[i])); ASCIIEncoding asen = new ASCIIEncoding(); s.Send(asen.GetBytes("RECEIVED :")); i want to get something like String GETSTRING; byte[] b = new byte[100]; int k = s.Receive(b); Console.WriteLine("Recieved..."); for (int i = 0; i < k; i++) Console.Write(Convert.ToChar(b[i])); GETSTRING = *WHATEVER RESPONSE RECEIVED ABOVE* ASCIIEncoding asen = new ASCIIEncoding(); s.Send(asen.GetBytes("RECEIVED :"));

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  • Poblem with "CFDataRef".

    - by zp26
    Hello I have a problem with "CFDataRef. I get the "data" field from a "kCFSocketDataCallBack. "data" should correspond to a string received on the socket. How do I convert, for example, in a NSString so I can put my text in a textbox?? Thank you very much static void AcceptDataCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { //my code for the textBox }

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  • Can two different UDP socket in a system bind same port?

    - by swift
    I have an application which uses UDP connection, now when i try to run the app more than once its throwing me an exception java.net.BindException: Address already in use: Cannot bind but in my another app, which uses tcp connection, i can open two instance of the same app and its working fine. why this error only with UDP connection?

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  • [Java] Listening for TCP and UDP requests on the same port

    - by user339328
    I am writing a Client/Server set of programs Depending on the operation requested by the client, I use make TCP or UDP request. Implementing the client side is straight-forward, since I can easily open connection with any protocol and send the request to the server-side. On the servers-side, on the other hand, I would like to listen both for UDP and TCP connections on the same port. Moreover, I like the the server to open new thread for each connection request. I have adopted the approach explained in: link text I have extended this code sample by creating new threads for each TCP/UDP request. This works correctly if I use TCP only, but it fails when I attempt to make UDP bindings. Please give me any suggestion how can I correct this. tnx

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  • C socket and openssl (RSA)

    - by giozh
    there's something strange in my client/server socket using RSA. If i test it on localhost, everithing goes fine, but if i put client on a pc and server on othe pc, something gone wrong. Client after call connect, call a method for public keys exchange with server. This part of code works fine. After this, client send a request to server: strcpy(send_pack->op, "help\n"); RSA_public_encrypt(strlen(send_pack->op), send_pack->op, encrypted_send->op, rsa_server, padding); rw_value = write(server, encrypted_send, sizeof (encrypted_pack)); if (rw_value == -1) { stampa_errore(write_error); close(server); exit(1); } if (rw_value == 0) { stampa_errore(no_response); close(server); exit(1); } printf("---Help send, waiting for response\n"); set_alarm(); rw_value = read(server, encrypted_receive, sizeof (encrypted_pack)); alarm(0); if (rw_value == -1) { stampa_errore(read_error); exit(1); } if (rw_value == 0) { stampa_errore(no_response); close(server); exit(1); } RSA_private_decrypt(RSA_size(rsa), encrypted_receive->message, receive_pack->message, rsa, padding); printf("%s\n", receive_pack->message); return; } but when server try to decrypt the receive message on server side, the "help" string doesn't appear. This happen only on the net, on localhost the same code works fine... EDIT: typedef struct pack1 { unsigned char user[encrypted_size]; unsigned char password[encrypted_size]; unsigned char op[encrypted_size]; unsigned char obj[encrypted_size]; unsigned char message[encrypted_size]; int id; }encrypted_pack; encrypted_size is 512, and padding used is RSA_PKCS1_PADDING

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  • How to open multiple socket connections and do callbacks in PHP

    - by Click Upvote
    I'm writing some code which processes a queue of items. The way it works is this: Get the next item flagged as needing to be processed from the mysql database row. Request some info from a google API using Curl, wait until the info is returned. Do the remainder of the processing based on the info returned. Flag the item as processed in the db, move onto the next item. The problem is that on step # 2. Google sometimes takes 10-15 seconds to return the requested info, during this time my script has to remain halted and wait. I'm wondering if I could change the code to do the following instead: Get the next 5 items to be processed as usual. Request info for items 1-5 from google, one after the other. When the info for item 1 is returned, a 'callback' should be done which calls up a function or otherwise calls some code which then does the remainder of the processing on items 1-5. And then the script starts over until all pending items in db are marked processed. How can something like this be achieved?

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  • recvfrom() return values in Stop-and-Wait UDP?

    - by mavErick
    I am trying to implement a Stop-and-Wait UDP client-server socket program in C. As known, there are basically three possible scenarios for Stop-and-Wait flow control. i.e., After transmitting a packet, the sender receives a correct ACK and thus starts transmitting the next packet; the sender receives an incorrect ACK and thus retransmits this packet; the sender receives no ACK within a TIMEOUT and thus retransmits this packet. My idea is to differentiate these three scenarios with the return value of recvfrom() on the sender side. For scenario 1&2: recvfrom() just returns the length of the received ACK. Since in my implementation the incorrect ACK is of the same length of the correct one, so I will have to go deeper and check the contents of the ACK. It's not a big deal. I know how to do. Problems come when I am trying to recognize scenario 3 where no ACK is received. What confuses me is that my recvfrom() is within a while loop, so the recvfrom() will be called constantly. What will it return when the receiver is not actually sending the sender ACK? Is it 0 or 1?

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  • How to identify end of InputStream in java

    - by Vardhaman
    I am trying to read bytes from server using Socket program, ie I am using InputStream to read the bytes. If I pass the length size I am able to read the bytes, but I am not sure what may be the length. So I am not able initialize the byte array. Also I tried while (in.read() !=-1), I observered it loop works fine when the data is sent , but the next line after the loop is not executable , I feel its still looking for the data in the stream but there is no ata. If I close the Server connection , then my client will execute the next line followed to the loop. I am not sure where I am going wrong? this.in = socket.getInputStream(); int dataInt = this.in.read(); while(dataInt != -1){ System.out.print(","+i+"--"+dataInt); i++; dataInt = this.in.read(); } System.out.print("End Of loop"); I get the output as:- ,1--0,2--62,3--96,4--131,5--142,6--1,7--133,8--2,9--16,10--48,11--56,12--1,13--0,14--14,15--128,16--0,17--0,18--0,19--48,20--0,21--0,22--0,23--0,24--0,25--1,26--0,27--0,28--38,29--114,30--23,31--20,32--70,33--3,34--20,35--1,36--133,37--48,38--51,39--49,40--52,41--49,42--55,43--49,44--52,45--52,46--54,47--55,48--50,49--51,50--52,51--48,52--53,53--56,54--51,55--48,56--48,57--57,58--57,59--57,60--57,61--57,62--57,63--57,64--56 But no output for :- End Of loop Please guide how shall I close the loop? Looking forward for you response. Thanking you all in advance.

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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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