This module provides access to the BSD socket interface. It is available on all modern Unix systems, Windows, MacOS, BeOS, OS/2, and probably additional platforms.
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 platform-specific reference material for the various socket-related system calls are also a valuable source of information on the details of socket semantics. For Unix, refer to the manual pages; for Windows, see the WinSock (or Winsock 2) specification.
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 higher-level than in the C interface: as with read() and 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.
For IP addresses, two special forms are accepted instead of a host
address: the empty string represents INADDR_ANY, and the string
'<broadcast>' represents INADDR_BROADCAST.
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 socket.error.
Non-blocking mode is supported through the setblocking() method.
The module socket exports the following constants and functions:
(errno, string)representing an error returned by a system call, similar to the value accompanying os.error. See the module errno, which contains names for the error codes defined by the underlying operating system.
'126.96.36.199'. If the host name is an IP address itself it is returned unchanged. See gethostbyname_ex() for a more complete interface.
(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 (often but not always a single address).
gethostbyname(gethostname()). Note: gethostname() doesn't always return the fully qualified domain name; use
(hostname, aliaslist, ipaddrlist)where hostname is the primary host name responding to the given ip_address, aliaslist is a (possibly empty) list of alternative host names for the same address, and ipaddrlist is a list of IP addresses for the same interface on the same host (most likely containing only a single address). To find the fully qualified domain name, check hostname and the items of aliaslist for an entry containing at least one period.
'icmp') to a constant suitable for passing as the (optional) third argument to the socket() function. This is usually only needed for sockets opened in ``raw'' mode (SOCK_RAW); for the normal socket modes, the correct protocol is chosen automatically if the protocol is omitted or zero.