When a new Socket is created new port number should be allocated.

When the service on the same socket is changed, a new port number should be alloted.

Note :- Some alloted port numbers :

port no. Application

13                                    Date and time Services

21                                    FTP,Which transfers files

23                                   Telnet,Which provides remote login

25                                   SMTP,Which delivers mail messages

67                                   BOOTP,Which provides configuration at  boot time

80                                  HTTP, Which transfers web pages

109                          POP,Whcih enables users to access mail boxes on remote sys.

for port no Internally 2 bytes is used

NOTE:

1) To create Server Socket, ServeerSocket class is avialable in java.net.package

2) To create Client Socket Socket class is available in java.net.package