multithreading - chat in java not synchronized (sockets, threads) -

i'm trying figure out way instance of server negotiate between 2 clients creating chat thread between them.

i created project, , "almost" works... seems there buffer of synch problem.

when writing line in 1 side (i.e client#1), doesn't pass other side (i.e client#2), after client#2 trys pass line too.

i know there might better ways implement this, i'd understand what's wrong my code.

your great!

the code:

server

import java.io.*; import java.net.*;  public class server {     public static void main(string[] args)     {         int id = 1;          system.out.println();         system.out.println("server");          try         {            serversocket serversocket = new serversocket(4321);              while (true)             {                 socket client1socket = serversocket.accept();                 socket client2socket = serversocket.accept();                  system.out.println("clients connected ports: \n"                         + client1socket.getport() + ", " + client2socket.getport());                  thread client1thread = new serverthread(client1socket, client2socket, id);                 client1thread.start();                 id++;                  thread client2thread = new serverthread(client2socket, client1socket, id);                 client2thread.start();                 id++;             }         }          catch (ioexception ioe)          {             ioe.printstacktrace();         }     } } 

server thread

import java.io.*; import java.net.*; import java.util.*;  public class serverthread extends thread  {     socket sourcesocket;     socket destsocket;     int id;      public serverthread(socket src, socket dst, int n)      {         sourcesocket = src;         destsocket = dst;         id = n;     }      public void run()      {         try         {             scanner clientinput = new scanner(sourcesocket.getinputstream());             printstream destoutput = new printstream(destsocket.getoutputstream());             destoutput.println("you chatting client " + id);              boolean more = true;             while (more)              {                 string input = clientinput.nextline();                 destoutput.println(input);                  if (input.equals("q"))                 {                     more = false;                 }             }             sourcesocket.close();             destsocket.close();         }         catch (ioexception ex)          {             ex.printstacktrace();         }     } } 

client

import java.io.*; import java.net.*; import java.util.*;  public class client  {     public static void main(string[] args)      {         system.out.println();         system.out.println("client");          try         {             socket clientsocket = new socket("localhost", 4321);              system.out.println("connection established");             scanner input = new scanner(clientsocket.getinputstream());             printstream output = new printstream(clientsocket.getoutputstream());             scanner in = new scanner(system.in);              system.out.println(input.nextline());              boolean more = true;              while (more)              {                 string text = in.nextline();                 output.println(text);                 string nextinput = input.nextline();                  if (nextinput == null)                  {                     more = false;                 }                 else                  {                     system.out.println(nextinput);                 }             }         }         catch (ioexception ex)          {             ex.printstacktrace();         }     } } 

in client code, line string text = in.nextline(); block thread. means if never type in in client, can not receive anything. solution put message receiving code in thread. such as:

    thread thread = new thread(new runnable() {                      @override                     public void run() {                         // todo auto-generated method stub                         while (!thread.interrupted()) {                             system.out.println(input.nextline());                         }                     }                  });                 thread.start();                  while (true)                  {                     string text = in.nextline();                     output.println(text); //                string nextinput = input.nextline();                     ......................                 }