//package mv3500code; import java.io.*; import java.net.*; /** * Very slightly more complex than example1. A complete copy of * example 2. The only thing this does * differently is introduce a loop into the response, so you don't * have to restart the program after one response. Also, it prints * out the socket pair the server sees. Run the program via telnet * several times and compare the socket pairs. * * telnet localhost 2317 * * If you're sophisticated you can contact the instructor's computer * while running this program. * * telnet <ipOfServersLaptop> 2317 * * And have him display the socket pairs he got. * @author mcgredo */ public class BlankenbekerMyTcpServer { public static void main(String[] args) { try { // ServerSocket waits for a connection from a client. // Notice that it is outside the loop; ServerSocket // needs to be made only once. int connectionCount = 0; ServerSocket serverSocket = new ServerSocket(2317); // Loop, infinitely, waiting for client connections. // Stop the program somewhere else. while(true) { Socket clientConnection = serverSocket.accept(); OutputStream os = clientConnection.getOutputStream(); PrintStream ps = new PrintStream(os); connectionCount++; ps.println("This was written by the server"); InputStream is = clientConnection.getInputStream(); InputStreamReader isr = new InputStreamReader(is); BufferedReader br = new BufferedReader(isr); String serverMessage = br.readLine(); System.out.println("The message the client sent was " + serverMessage); // Print some information locally about the Socket // connection. This includes the port and IP numbers // on both sides (the socket pair.) InetAddress localAddress = clientConnection.getLocalAddress(); InetAddress remoteAddress = clientConnection.getInetAddress(); int localPort = clientConnection.getLocalPort(); int remotePort = clientConnection.getPort(); // My socket pair connection looks like this, to localhost: // Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54876 )) // Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 )) // // Why is the first IP/port the same, while the second set has // different ports? System.out.println("Socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( " + remoteAddress.toString() + ", " + remotePort + " ))"); System.out.println("Connection count is: " + connectionCount); // Notice the use of flush() and close(). Without // the close() to Socket object may stay open for // a while after the client has stopped needing this // connection. Close() explicitly ends the connection. ps.flush(); clientConnection.close(); } } catch(Exception e) { System.out.println("problem with networking"); } } }