Multithreaded Proxy Server implemented in java -

i implementing multithreaded proxy server in java accept messages clients , forward them server acknowledge reception of message. however, i'm having trouble doing so. point out doing wrong? thanks.

proxyapp:

public class proxyapp {      public static serversocket server = null;     public static socket client = null;       public static void main(string[] args)     {         try         {             server = new serversocket(6789);             socket clientsocket = null;              while(true)             {                  client = server.accept();                        if(client.isconnected())                 {                     system.out.println("proxy listening client on port 6789");                 }                 thread t1 = new proxyhandler(client);                 t1.start();                  clientsocket = new socket(inetaddress.getlocalhost(), 6780);                 if(clientsocket.isbound())                 {                     system.out.println("clientsocket connected on port 6780");                 }                  proxyhandler t2 = new proxyhandler(clientsocket);                 t2.start();                                                                            }         }         catch(ioexception io)         {             system.err.println("ioexception: " + io.getmessage());         }     } } 

proxyhandler:

public class proxyhandler extends thread {      private socket socket;     private string message;      public proxyhandler(socket socket)     {         this.socket = socket;             }      @override     public void run()     {                message = "";         try         {             datainputstream in = new datainputstream(socket.getinputstream());             dataoutputstream out = new dataoutputstream(socket.getoutputstream());             while(true)             {                 message = in.readutf();                 out.writeutf(message);                  system.out.println(message);             }         }         catch(ioexception io)         {             system.err.println("ioexception: " + io.getmessage());             system.exit(2);         }     } } 

clientclass:

public class clientclass {      public static void main(string[] args)     {         try         {             socket client = new socket(inetaddress.getlocalhost(), 6789);              if(client.isbound())             {                 system.out.println("successfully connected on port 6789");             }              scanner scanner = new scanner(system.in);              datainputstream infromproxy = new datainputstream(client.getinputstream());             dataoutputstream outtoproxy = new dataoutputstream(client.getoutputstream());              while(true)             {                 string message;                  system.out.print("enter message: ");                 message = scanner.next();                  outtoproxy.writeutf(message);                 system.out.println(infromproxy.readutf());             }         }         catch(ioexception io)         {             system.err.println("ioexception: " + io.getmessage());             system.exit(2);         }     } } 

serverclass:

public class serverclass {      public static void main(string[] args)     {         try         {             serversocket server = new serversocket(6780);              if(server.isbound())             {                 system.out.println("server connected on port 6780");             }              socket client = null;             while(true)             {                 client = server.accept();                  if(client.isconnected())                 {                     system.out.println("proxy connected");                 }                  datainputstream infromproxy = new datainputstream(client.getinputstream());                 dataoutputstream outtoproxy = new dataoutputstream(client.getoutputstream());                  system.out.println(infromproxy.readutf());                  outtoproxy.writeutf("message has been acknowledged!");             }             }         catch(ioexception io)         {             system.err.println("ioexception: " + io.getmessage());             system.exit(2);         }     } } 

the in , out in following code represent message , same machine:

datainputstream in = new datainputstream(socket.getinputstream()); dataoutputstream out = new dataoutputstream(socket.getoutputstream()); 

so when read in , write out, doing creating echo service.

message = in.readutf(); out.writeutf(message); 

for proxy, want read client , write server, , vice versa.

it seems want closer this:

    client = server.accept();           clientsocket = new socket(inetaddress.getlocalhost(), 6780);     thread t1 = new proxyhandler(client, clientsocket );     t1.start();     thread t2 = new proxyhandler(clientsocket, client);     t2.start(); 

where job of first thread send data client server , second's job send server client.