Socket Programming-Advanced Computer Programminng-Lab Lecture, Lecture notes of Java Programming

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Networking

Socket programming

Socket

 A socket is a endpoint of a two-way communication link between two programmes running on the network

 Socket is a bidirectional communication channel between hosts( a computer on a network can be termed as a host)

Communication link

Socket (endpoints)

Socket’s Dynamics

 A socket is an abstraction of the network similar to the way a file is an abstraction of system’s hard drive.  We store and retrieve data through files from hard drive without knowing the actual dynamics of the hard drive.  Similarly we send and receive data to and from network through socket without actually going into underlying mechanics.

Sending/Receiving Messages

through socket

 We read from or write data to a file using streams.  Similarly to read from or write data to a socket, we use streams 

What is a port

 Transport address to which processes can listen for connection requests  Computer can listen on that specific transport address where some request is being sent.  Local to host: 64k TCP and 64k UDP ports  Well known ports  Below 1024  Standard services

Steps to make a simple client

 Import required packages  Connect/open a socket with server  Get I/O streams of socket  Send/ Receive message  Close socket

Cont…

 Send/ Receive message  pw.println(“hello”);  String recieveMsg=br.readLine();  Close socket  S.close();  Br.close();  Pw.close();

Steps to make a simple server

 Import required packages  Create a Server socket  Wait for incoming connection  Get I/O streams of communication socket  Send/ Receive message  Close socket

 Get I/O streams of socket

 InputStream is=s.getInputStream()  InputStreamReader isr=new InputStreamR(is);  BufferedReader br=new BufferedReader(isr);  OutputStream os=s.getOutputStream()  PrintWriter pw=new PrintWriter(os,true)

Cont…

 Send/ Receive message  pw.println(“hello”);  String recieveMsg=br.readLine();  Close socket  S.close();  Br.close();  Pw.close();