Hands On NetworkingSocket Programming

Ram P Rustagi, ISE Deptrprustagi@pes.edu

Abhishek Gupta, ISE DeptLaxmi Kuber, MCA Dept

June 28-30, 2012

Socket programming

• Sockets– Protocol independent method of creating a connection

a connection– Can be either

• Connection based or connection less– Connection established before communication– Destination information provided with each

packet– Packet based or stream based

• Message boundaries vs one stream– Reliable vs unreliable

• Message recovered in case– Loss, duplication, corruption, out of order delivery

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Socket programming

• Ports– Three categories– Well known ports

• Assigned and managed by IANA• Ranges from 1 1023

– Registered ports• Can be registered by IANA• Ranges from 1024 to 49151

– Dynamic ports• Free to be used by application at will

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Socket characteristics

• Sockets are charaterized by– Domain, type and transport protocol

• Common domains are– AF-UNIX– AF_INET– AF_INET6

• Types are– Datagram vs streams

• Transport protocols– TCP– UDP

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Socket Programming

• Server side – Concurrent connections handling

• Multi processing• Single threaded using select(), poll()• Non-blocking communication

• WE-1– Simple client server programming (using C)

• WE-2– Multi-processing server side programming

• WE-3– Server side single threaded concurrent connections

• Using select()• Using poll()

• WE-4– Using non-blocking I/O

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Socket Programming

• Socket programming concepts– Client side and server side differences– Well known ports, reserved ports and ephemeral ports– UDP vs TCP programming

• Client side programming– Socket()– Connect() // only for TCP– Read(), write()– Close()

• Server side programming– Socket()– Bind()– Listen()– Accept()– Read(), write()– Close() 6

Socket API’s• socket: creates a socket of a given domain, type,

protocol (buy a phone)

• bind: assigns a name to the socket (get a telephone number)

• listen: specifies the number of pending connections that can be queued for a server socket. (call waiting allowance)

• accept: server accepts a connection request from a client (answer phone)

• connect: client requests a connection request to a server (call)

• send, sendto: write to connection (speak)• recv, recvfrom: read from connection (listen)• shutdown: end the call

socket

Bind

Listen

accept

Send/recv

Close

shutdown

close

socket

connect

Send/recv

shutdown

close

server client

Non-Blocking I/O

• Programs that use non-blocking I/O– every function has to return immediately– Can not wait or get blocked

• To make a non-blocking program– make the socket non-blocking– ioctl(sockfd, FIONBIO, (char *)&on);

programs

• WE-1– Simple client/server programs– Sample given for both in C and Java

• WE-2– multi-processing server side– C –based, server creates a child for each connection– Java based, server creates a thread for each connection

• WE-3– Available only for C based– Use of select

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