This module provides access to the BSD socket interface. It is available on Unix systems that support this interface.
For an introduction to socket programming (in C), see the following papers: An Introductory 4.3BSD Interprocess Communication Tutorial, by Stuart Sechrest and An Advanced 4.3BSD Interprocess Communication Tutorial, by Samuel J. Leffler et al, both in the Unix Programmer's Manual, Supplementary Documents 1 (sections PS1:7 and PS1:8). The Unix manual pages for the various socket-related system calls are also a valuable source of information on the details of socket semantics.
The Python interface is a straightforward transliteration of the
Unix system call and library interface for sockets to Python's
object-oriented style: the
socket() function returns a
socket object whose methods implement the various socket system
calls. Parameter types are somewhat higer-level than in the C
interface: as with
write() operations on Python
files, buffer allocation on receive operations is automatic, and
buffer length is implicit on send operations.
Socket addresses are represented as a single string for the
AF_UNIX address family and as a pair
(host, port) for the
AF_INET address family,
where host is a string representing
either a hostname in Internet domain notation like
'daring.cwi.nl' or an IP address like
and port is an integral port number. Other address families are
currently not supported. The address format required by a particular
socket object is automatically selected based on the address family
specified when the socket object was created.
All errors raise exceptions. The normal exceptions for invalid
argument types and out-of-memory conditions can be raised; errors
related to socket or address semantics raise the error
Non-blocking mode is supported through the
socket exports the following constants and functions:
(errno, string)representing an error returned by a system call, similar to the value accompanying
socket(). If the
AF_UNIXconstant is not defined then this protocol is unsupported.
SOCK_DGRAMappear to be generally useful.)
getsockoptmethods of socket objects. In most cases, only those symbols that are defined in the Unix header files are defined; for a few symbols, default values are provided.
'220.127.116.11'. If the host name is an IP address itself it is returned unchanged.
(hostname, aliaslist, ipaddrlist)where
hostnameis the primary host name responding to the given ip_address,
aliaslistis a (possibly empty) list of alternative host names for the same address, and
ipaddrlistis a list of IP addresses for the same interface on the same host (most likely containing only a single address).
AF_UNIX. The socket type should be
SOCK_DGRAMor perhaps one of the other `SOCK_' constants. The protocol number is usually zero and may be omitted in that case.
filenomethod). Address family, socket type and protocol number are as for the
socketfunction above. The file descriptor should refer to a socket, but this is not checked -- subsequent operations on the object may fail if the file descriptor is invalid. This function is rarely needed, but can be used to get or set socket options on a socket passed to a program as standard input or output (e.g. a server started by the Unix inet daemon).