1. Socket Programming
Cal Poly Pomona Young CS380

2. IP Address Port Number What is a socket ? Wh
A socket is one endpoint of a two-way communication link between two programs running on the network, which consists of
IP Address
AND
Port Number
CS380
Socket Programming

3. What do sockets do? Sockets TCP connection Server Client
allows programs on different machines send data to one another
CS380
Socket Programming

4. How to establish connections?
Server Side:
Create Server Socket
Bind the Server Socket to a specific port
Listen for incoming connection requests
Accept requests and bind new sockets to different port numbers, then go back to listen
Remarks:
are reserved (well-known) port which are used only by OS
CS380
Socket Programming

5. How to establish connections?
Client Side:
Create Socket
Connect using IP Address and Port Number of the server process
The port number used by client locally is allocated by OS dynamically
CS380
Socket Programming

6. How to establish connections?
.....
Server
Process
Client
Server machine A
Client machine B
Ports
Connection
Request to (A,n) n
Server creates Server Socket and listen to port number n
Client creates Socket
Client connects socket to machine A at port n
Server rebind new connections to different ports and continue to listen
CS380
Socket Programming

7. How to establish connections?
.....
Server
Process
Client
Server machine A
Client machine B
Ports n
TCP connection established!!
CS380
Socket Programming

8. Socket in Java Server Side ServerSocket, Socket
ServerSocket ss = new ServerSocket(port);
Socket s = ss.accept();
CS380
Socket Programming

9. Socket in Java Client Side: Socket
Socket s = new Socket(hostname,port);
CS380
Socket Programming