I need to build a proxy server that will keep alive an asynchronous
connection with a client and a remote server until the client closes. The
type of data is ASCII.

I've tried this code it doesn't work?

//needs to keep client socket & server socket open and wait for messages
from client and returns from server

class CommSession extends Thread{
Socket clie;
Socket serv;
       CommSession(Socket clie,Socket serv){
               this.clie=clie;
               this.serv=serv;
       }

       public void run(){

               try{
               System.out.println("set up session on "+serv);
               while(!clie.isClosed()){
                       DataInputStream in = new
DataInputStream(clie.getInputStream());
                       DataOutputStream out = new
DataOutputStream(serv.getOutputStream());
                       String cmd="";
                       while((cmd=in.readLine())!=null){
                               out.writeBytes(cmd+"\n");
                               System.out.println("TO-SERVER:"+cmd);
                       }

                       DataInputStream in2 = new
DataInputStream(serv.getInputStream());
                       DataOutputStream out2 = new
DataOutputStream(clie.getOutputStream());
                       String cmd2="";
                       while((cmd2=in2.readLine())!=null){
                               out2.writeBytes(cmd2+"\n");
                               System.out.println("TO-CLIENT:"+cmd2);
                       }

               }

               }catch(Exception ss){ss.printStackTrace();}
       }

}