Unix sockets

Unix sockets provide a way to send data between processes and network interfaces.

A socket connection has a protocol and an address. For internet communication, addresses are composed of an IP address and a port. Computers can open multiple connections to and from the same addresses using different ports.

There are several functions used to manipulate sockets:

• socket: Creates an endpoint for communication and returns its associated file-descriptor.
• setsockopt: Set socket stream options.
• getsockopt: Get socket stream options.
• getsockname: Get the socket's associated name.
• bind: Bind a socket to a name.
• connect: Initiate a connection to another socket's address.
• listen: Listen for incoming socket connections on the bound address.
• accept: Accept an incoming socket connection and get an associated file-descriptor.
• send: Write data to a socket stream.
• recv: Read incoming data from a socket stream.

There are several functions used to manipulate network format numbers:

• htons, htonl: Convert values from host to network byte order.
• ntohs, ntohl: Convert values from network to host byte order.
• inet_aton, inet_addr, inet_network: Interpret strings representing numbers in the internet standard '.' notation.
• inet_pton: Convert a presentation format address to network format.
• inet_aton: Interpret string as an internet address.
• inet_ntop: Convert an address from network format to presentation format.
• getprotobyname: Get a network protocol by name.
• gethostbyname: Get a network host's address from its hostname.
• getaddrinfo: A more flexible replacement to gethostbyname and getservbyname.
• freeaddrinfo: Releases memory allocated by getaddrinfo.