Socket Programming

Introduction

Socket Definition• A network socket is one endpoint in a two-way

communication flow between two programs running over a network.

• A socket is bound to a port number so that the TCP layer can identify the application that data is destined to be sent to.

• Sockets are created and used with a set of programming requests or "function calls" sometimes called the sockets application programming interface (API). The most common sockets API is the Berkeley UNIX C interface for sockets.

• Sockets can also be used for communication between processes within the same computer.

Socket Definition (Cont)

• An endpoint is a combination of an IP address and a port number. Every TCP connection can be uniquely identified by its two endpoints. That way you can have multiple connections between your host and the server.

Socket Types• A socket is created address domain specified socket type specified• Two processes communicate iff same sockets type and same

domain. Adress Domains:

– Unix domain:• Processes share a common file system.• The address is a character string which is basically an entry in the file system.

– Internet domain:• Each process has its own address format.• The address is the host machine (IP address, port number). • Port numbers are 16 bit unsigned integers. • The lower numbers are reserved in Unix for standard services

Socket Types

Port Service

1 TCP port service multiplexer

7 Echo server

21 FTP server

23 Telnet server

80 HTTP server

Socket Types

Socket types:– stream sockets:

• treat communications as a continuous stream of characters• use TCP (Transmission Control Protocol), • which is a reliable.• stream oriented protocol.

– datagram sockets: • read entire messages at once.• use UDP (Unix Datagram Protocol).• which is unreliable.• message oriented.

Socket Programming

• TCPSocket = socket(PF_INET, SOCK_STREAM, 0)

• send()• recv()

• UDPSocket = socket(PF_INET, SOCK_DGRAM, 0)

• sendto()• recvfrom()