TCP Sockets

• JabberServer:

Very simple server that just echoes whatever the client sends.
 
1. create a server socket
ServerSocket s = new ServerSocket(PORT);
2. accept a client connection
Socket socket = s.accept();
3. get socket input stream
in = socket.getInputStream();
4. get socket output stream
out = socket.getOutputStream();
5. read
String str = in.readLine();
6. write
out.println(str);
 
• JabberClient:

Very simple client that just sends lines to the server and reads lines that the server sends.
 
 
1. create  a client  socket connected to the server
Socket socket = new Socket(addr, PORT);
2. get socket input stream
in = socket.getInputStream();
3. get socket output stream
out = socket.getOutputStream();
4. write
out.println(str);
5. read
String str = in.readLine();
 
 
How to run:
 
%java JabberServer

%java JabberClient localhost

• MultiJabberServer:

A server that uses multithreading to handle any number of clients.
 
1. For each client connection accepted in socket, create a thread to handle it:
new ServeOneJabber(socket);
2. The thread will get in/out streams from socket to read/write
• MultiJabberClient:

Client that tests the MultiJabberServer by starting up multiple clients.
 
1. Create many clients up to MAX_THREADS and sleep 100 ms
after the creation of each client.

while(true) {

      if (JabberClientThread.threadCount() < MAX_THREADS)
               new JabberClientThread(addr);
      Thread.currentThread().sleep(100);
}

2. Each client sends 25 messages to the server and exits.

for(int i = 0; i < 25; i++) {
        out.println("Client " + id + ": " + i);
        String str = in.readLine();
        System.out.println(str);
      }
out.println("END");
 

How to run:
 
%java MultiJabberServer

%java MultiJabberClient localhost
    (Type CTRL-C to interrupt).

UDP Sockets

• Dgram:

A utility class to convert back and forth between Strings and DatagramPacket.
    DatagramPacket toDatagram (String s, InetAddress destIA, int destPort)
     String toString (DatagramPacket p)
 
• ChatterServer:

A server that echoes received datagrams
 
DatagramSocket socket = new DatagramSocket(PORT);
socket.receive(dp);
String rcvd = String(dp.getData(),     0,   dp.getLength())  +
                                       dp.getAddress() +  dp.getPort();
socket.send(dp);

 
• ChatterClient:

Tests the ChatterServer by starting 10 clients, each of which sends/recieves 25 datagrams to the server. The code of each cleint is outlined as:
 
DatagramSocket s = new DatagramSocket();
s.send (dp);
s.receive (dp);
 
How to run:
 
%java  ChatterServer

%java  ChatterClient localhost

Multicasting

Receiving multicast message

For a process to recieve multicast messages it needs to perform the following steps:

1. Craeate a UDP socket ms

MulticastSocket ms = new MulticastSocket(port);

Bind ms it to  port, e.g., 1234.     All processes must bind to the same port in order     to receive the multicast messages.

2. Join a multicast group address group ,
    e.g., 224.111.112.113

ms.joinGroup(group);

3. Use recive  to read the messages, e.g.,

DatagramPacket recv = new DatagramPacket(buf, buf.length);
ms.receive(recv);

Sendinging multicast message

For a process to send  multicast messages it needs to
perform the following:

You may use the  socket ms for sending multicast messages or you can use  any other udp socket (it does not have to join any multicast group):

   DatagramPacket dp = new DatagramPacket(buf, buf.length(), group, port);
   ms.send(dp);
 
 

Time-to-live:

To control how far the messages can go,
e.g., 2 means at most 2 routers away.

ms.setTimeToLive(2);
 

Loopback Control:

To let the application get a copy of its own transmission:

 
ms.setLoopbackMode(true);
 

Multicast Example

 mchat.java

        Usage: java mchat <mgrp> <port>

        Example: java mchat  224.2.2.2   1234