networking - Why port 80 is used for server applications? -

i want develop enterprise application wherein each employee has client application , there common server has server application. client , server exchanging information in form of text, image files, zip files, etc. research think tcp best protocol. not understand how assign port numbers. here understanding far.

• client can have random port selected automatically os. need query os getting port number client?
• server port number has hard coded in server , client application.
• server port number should 80. why? possible have other port number server application? if yes how select it?
• what happens if port number used server being used other application on server?

edit: following of articles/questions gave me impression port 80 default port server.

• how multiple clients connect simultaneously 1 port, 80, on server?
• freeing tcp/ip port?
• http://computer.howstuffworks.com/web-server8.htm
• http://www.thomas-krenn.com/en/wiki/check_tcp_port_80_%28http%29_with_telnet

client can have random port selected automatically os. need query os getting port number client?

yes. don't have query os this. call system function connect() , os take care of low level port number details you. note client not need know port running on. server knows client port number once tcp connection made.

server port number has hard coded in server , client application?

yes, 1 way it.

server port number should 80. why? , cannot there other port number?

it not have 80. can long port number known client. talking standard port number http servers. not apply private application.

what happens if port number used server being used other application on server?

once have designed system need make sure port number chose server free on server host. easy do. choose server port in range 49152 – 65535. these non registered ports can used private use. make sure not running private application on same port on server host.