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Multithreaded tcp/ip server in Java
Network Programming example from a Well House Consultants training course
More on Network Programming [link]
Source code: Leanne.java Module: J808
/* This is an example of a multithreaded server in Java.
It listens for connections on port 1357 (use telnet to make such connections once you have the server running) and echos any information sent to it to anyone else who's logged in at the time - a very simple talker application. See also http://www.wellho.net/solutions/java-a-multithreaded-server-in-java.html */ import java.net.*; import java.io.*; import java.util.*; public class Leanne implements Runnable { // A simple talker - Sample written by Graham Ellis, July 2010 (update) // No login needed. Connect on port 1357. // commands: // .q quit // .w who // Variables for each thread Socket linkto; // the socket PrintWriter out; // the output and input streams BufferedReader in; int id; // i.d. of the connection String from_name; // name of host connecting // Class Variables static Vector connectiontable; // current connections static int nextid = 1; // Increasing i.d. /////////////////////////////// Main method //////////////////////// public static void main(String [] args) { // Parent thread - create a server socket and await a connection ServerSocket ss = null; Socket s = null; connectiontable = new Vector(); try { ss = new ServerSocket(1357); while ((s=ss.accept())!= null) { // Connection received - create a thread Leanne now; Thread current = new Thread(now = new Leanne(s)); current.setDaemon(true); connectiontable.addElement(now); // Save talker into vector .. current.start(); // start the user's thread } } catch (Exception e) { System.out.println(e); } // should add finally block to close down } ///////////////// Constructor for a new thread ////////////////////// Leanne (Socket from) { id = nextid++; linkto = from; InetAddress source = linkto.getInetAddress(); from_name = source.getHostName(); try { out = new PrintWriter(new OutputStreamWriter (linkto.getOutputStream())); in = new BufferedReader(new InputStreamReader (linkto.getInputStream())); } catch (Exception e) {} } public void run () { String line = " [User has just logged in] "; while (true) { boolean done=false; // read a line from the user if (line == null) { try { out.print(">: "); //prompt,flush,read out.flush(); line = in.readLine(); } catch (Exception e) { System.out.println(e); done = true; // force exit if there's a problem } } // Handle special cases - user input starts with "." // You get a NULL back if connection lost and we should // pick up that exception! try { if (line.startsWith(".q")) done = true; } catch (Exception e) { // e.g. null done = true; line = "[exiting]"; } if (line.startsWith(".w")) { // build up list of host names int k; StringBuffer fred = new StringBuffer("WHO HERE?\n"); for (k=0;k<connectiontable.size();k++) { Leanne person = (Leanne)connectiontable.elementAt(k); fred.append(person.from_name); fred.append(" "); } line = fred.toString(); } // echo the line (with a header) to all users String outline = from_name+" "+id+": "+line; int k; for (k=0;k<connectiontable.size();k++) { Leanne person = (Leanne)connectiontable.elementAt(k); person.out.println(outline); person.out.flush(); // Vital - ensure it is sent! } // clear out the user if they're done if (done) { connectiontable.removeElement(this); try { out.close(); // closes needed to terminate connection in.close(); // otherwise user's window goes mute linkto.close(); } catch (Exception e) {} break; } line = null; } } } Learn about this subject
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Other Examples
This example comes from our "Network Programming" training module. You'll find a description of the topic and some
other closely related examples on the "Network Programming" module index page.
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