Overview of SOCKETS(POSIX) functions

The following overview of the SOCKETS interface functions collects several functions together into task-oriented groups. The columns IPv4 and IPv6 indicate the address family (AF_INET and/or AF_INET6) in which the function involved is supported.

Function	Description	IPv4	IPv6
Setting up and shutting down connections over sockets
socket()	Create socket	x	x
bind()	Assign a name to a socket	x	x
connect()	Initiate a connection over a socket	x	x
listen()	Test socket for pending connections	x	x
accept()	Accept connection over a socket	x	x
close()	Close socket	x	x
shutdown()	Close full duplex connection	x	x
socketpair()	Create a pair of connected sockets	x
Transferring data between two sockets
read(), readv()	Receive a message from a connected socket	x	x
recv()	Receive a message from a connected socket	x	x
recvfrom()	Receive a message from a socket	x	x
recvmsg()	Receive a message from a socket	x	x
send()	Send a message from socket to socket over a connection	x	x
sendto()	Send a message from socket to socket	x	x
sendmsg()	Send a message from socket to socket	x	x
write(), writev()	Send a message from socket to socket over a connection	x	x
poll()	Multiplex input/output	x	x
select()	Multiplex input/output	x	x
Receiving information about sockets
getsockopt()	Get socket options	x	x
setsockopt()	Set socket options	x	x
getpeername()	Get name of communications partner	x	x
getsockname()	Get name of socket	x	x
Test configuration values
gai_strerror()	Get description of a getaddrinfo() error code	x	x
getaddrinfo()	Get information about host name, host address and services	x	x
gethostbyaddr()	Get names of reachable hosts	x
gethostbyname()	Get addresses of reachable hosts	x
gethostname()	Get name of current host	x	x
getipnodebyaddr()	Get host name belonging to an IPv4 or IPv6 address	x	x
getipnodebyname()	Get IPv4 or IPv6 addresses belonging to a host name	x	x
getnameinfo()	Get host and service name corresponding to IP address and port number	x	x
getnetbyaddr()	Get name of a net	x	x
getnetbyname()	Get net address	x	x
getprotobyname()	Get number of a protocol	x	x
getprotobynumber()	Get name of a protocol	x	x
getservbyname()	Get port number of a service	x	x
getservbyport()	Get name of a service	x	x
sethostent()	Open host database	x	x
gethostent()	Read entry from host database	x	x
endhostent()	Close host database	x	x
setnetent()	Open network database	x	x
getnetent()	Read entry from network database	x	x
endnetent()	Close network database	x	x
setprotoent()	Open protocol database	x	x
getprotoent()	Read entry from protocol database	x	x
endprotoent()	Close protocol database	x	x
setservent()	Open services database	x	x
getservent()	Read entry from services database	x	x
endservent()	Close services database	x	x
Manipulate Internet address
inet_addr()	Convert character string from dotted notation to integer value (Internet address)	x
inet_network()	Convert character string from dotted notation to integer value (subnetwork section)	x
inet_makeaddr()	Create Internet address from subnetwork section and subnetwork local address section	x
inet_lnaof()	Extract local network address in byte order of host from Internet host address	x
inet_netof()	Extract network number in byte order of host from Internet host address	x
inet_ntoa()	Convert Internet host address into a string conforming to normal Internet dotted notation	x
inet_pton()	Converts an IP address in dotted or colon notation to the corresponding binary address	x	x
inet_ntop()	Converts a binary IP address to dotted or colon notation	x	x
Utility functions
freeaddrinfo()	Release memory area for an addrinfo structure	x	x
freehostent()	Release memory area for a hostent structure	x	x
htonl()	Convert 32-bit fields from host to network byte order	x
htons()	Convert 16-bit fields from host to network byte order	x	x
ntohl()	Convert 32-bit fields from network to host byte order	x
ntohs()	Convert 16-bit fields from network to host byte order	x	x
Control functions
fcntl()	Control sockets	x	x
ioctl()	Control sockets	x	x

Test macros for AF_INET6

The following test macros for the AF_INET6 address family are defined in <netinet/in.h>.

The parameters p, p1 and p2 are in6_addr structures.

Function	Description
IN6_IS_ADDR_UNSPECIFIED (p)	IPv6 address = unspecified (0) ?
IN6_IS_ADDR_LOOPBACK (p)	IPv6 address = loopback ?
IN6_IS_ADDR_LINKLOCAL (p)	IPv6 address = linklocal ?
IN6_IS_ADDR_SITELOCAL (p)	IPv6 address = sitelocal ?
IN6_IS_ADDR_V4MAPPED (p)	IPv6 address = IPv4-mapped ?
IN6_IS_ADDR_V4COMPAT (p)	IPv6 address = IPv4-compatible ?
IN6_ARE_ADDR_EQUAL (p1, p2)	IPv6 address1 = IPv6 address2 ?