socket programming multiple client to one server
For every client you need to start separate thread. Example:
public class ThreadedEchoServer { static final int PORT = 1978; public static void main(String args[]) { ServerSocket serverSocket = null; Socket socket = null; try { serverSocket = new ServerSocket(PORT); } catch (IOException e) { e.printStackTrace(); } while (true) { try { socket = serverSocket.accept(); } catch (IOException e) { System.out.println("I/O error: " + e); } // new thread for a client new EchoThread(socket).start(); } }}and
public class EchoThread extends Thread { protected Socket socket; public EchoThread(Socket clientSocket) { this.socket = clientSocket; } public void run() { InputStream inp = null; BufferedReader brinp = null; DataOutputStream out = null; try { inp = socket.getInputStream(); brinp = new BufferedReader(new InputStreamReader(inp)); out = new DataOutputStream(socket.getOutputStream()); } catch (IOException e) { return; } String line; while (true) { try { line = brinp.readLine(); if ((line == null) || line.equalsIgnoreCase("QUIT")) { socket.close(); return; } else { out.writeBytes(line + "\n\r"); out.flush(); } } catch (IOException e) { e.printStackTrace(); return; } } }}You can also go with more advanced solution, that uses NIO selectors, so you will not have to create thread for every client, but that's a bit more complicated.
This is the echo server handling multiple clients... Runs fine and good using Threads
// echo serverimport java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;public class Server_X_Client {public static void main(String args[]){ Socket s=null; ServerSocket ss2=null; System.out.println("Server Listening......"); try{ ss2 = new ServerSocket(4445); // can also use static final PORT_NUM , when defined } catch(IOException e){ e.printStackTrace(); System.out.println("Server error"); } while(true){ try{ s= ss2.accept(); System.out.println("connection Established"); ServerThread st=new ServerThread(s); st.start(); } catch(Exception e){ e.printStackTrace(); System.out.println("Connection Error"); } }}}class ServerThread extends Thread{ String line=null; BufferedReader is = null; PrintWriter os=null; Socket s=null; public ServerThread(Socket s){ this.s=s; } public void run() { try{ is= new BufferedReader(new InputStreamReader(s.getInputStream())); os=new PrintWriter(s.getOutputStream()); }catch(IOException e){ System.out.println("IO error in server thread"); } try { line=is.readLine(); while(line.compareTo("QUIT")!=0){ os.println(line); os.flush(); System.out.println("Response to Client : "+line); line=is.readLine(); } } catch (IOException e) { line=this.getName(); //reused String line for getting thread name System.out.println("IO Error/ Client "+line+" terminated abruptly"); } catch(NullPointerException e){ line=this.getName(); //reused String line for getting thread name System.out.println("Client "+line+" Closed"); } finally{ try{ System.out.println("Connection Closing.."); if (is!=null){ is.close(); System.out.println(" Socket Input Stream Closed"); } if(os!=null){ os.close(); System.out.println("Socket Out Closed"); } if (s!=null){ s.close(); System.out.println("Socket Closed"); } } catch(IOException ie){ System.out.println("Socket Close Error"); } }//end finally }}Also here is the code for the client.. Just execute this code for as many times as you want to create multiple client..
// A simple Client Server Protocol .. Client for Echo Serverimport java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.InetAddress;import java.net.Socket;public class NetworkClient {public static void main(String args[]) throws IOException{ InetAddress address=InetAddress.getLocalHost(); Socket s1=null; String line=null; BufferedReader br=null; BufferedReader is=null; PrintWriter os=null; try { s1=new Socket(address, 4445); // You can use static final constant PORT_NUM br= new BufferedReader(new InputStreamReader(System.in)); is=new BufferedReader(new InputStreamReader(s1.getInputStream())); os= new PrintWriter(s1.getOutputStream()); } catch (IOException e){ e.printStackTrace(); System.err.print("IO Exception"); } System.out.println("Client Address : "+address); System.out.println("Enter Data to echo Server ( Enter QUIT to end):"); String response=null; try{ line=br.readLine(); while(line.compareTo("QUIT")!=0){ os.println(line); os.flush(); response=is.readLine(); System.out.println("Server Response : "+response); line=br.readLine(); } } catch(IOException e){ e.printStackTrace(); System.out.println("Socket read Error"); } finally{ is.close();os.close();br.close();s1.close(); System.out.println("Connection Closed"); }}}