7.2.1 Socket Objects
Keywords: lib

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7.2.1 Socket Objects

Socket objects have the following methods. Except for `makefile()` these correspond to Unix system calls applicable to sockets.

`accept` ()
  Accept a connection. The socket must be bound to an address and listening for connections. The return value is a pair `(conn, address)` where conn is a new socket object usable to send and receive data on the connection, and address is the address bound to the socket on the other end of the connection.

`bind` (address)
  Bind the socket to address. The socket must not already be bound. (The format of address depends on the address family -- see above.) Note: This method has historically accepted a pair of parameters for `AF_INET` addresses instead of only a tuple. This was never intentional and will no longer be available in Python 1.7.

`close` ()
  Close the socket. All future operations on the socket object will fail. The remote end will receive no more data (after queued data is flushed). Sockets are automatically closed when they are garbage-collected.

`connect` (address)
  Connect to a remote socket at address. (The format of address depends on the address family -- see above.) Note: This method has historically accepted a pair of parameters for `AF_INET` addresses instead of only a tuple. This was never intentional and will no longer be available in Python 1.7.

`connect_ex` (address)
  Like `connect(address)`, but return an error indicator instead of raising an exception for errors returned by the C-level `connect()` call (other problems, such as ``host not found,'' can still raise exceptions). The error indicator is `0` if the operation succeeded, otherwise the value of the `errno` variable. This is useful, e.g., for asynchronous connects. Note: This method has historically accepted a pair of parameters for `AF_INET` addresses instead of only a tuple. This was never intentional and will no longer be available in Python 1.7.

`fileno` ()
  Return the socket's file descriptor (a small integer). This is useful with `select.select()`.

`getpeername` ()
  Return the remote address to which the socket is connected. This is useful to find out the port number of a remote IP socket, for instance. (The format of the address returned depends on the address family -- see above.) On some systems this function is not supported.

`getsockname` ()
  Return the socket's own address. This is useful to find out the port number of an IP socket, for instance. (The format of the address returned depends on the address family -- see above.)

`getsockopt` (level, optname[, buflen])
  Return the value of the given socket option (see the Unix man page getsockopt(2)). The needed symbolic constants (`SO_*` etc.) are defined in this module. If buflen is absent, an integer option is assumed and its integer value is returned by the function. If buflen is present, it specifies the maximum length of the buffer used to receive the option in, and this buffer is returned as a string. It is up to the caller to decode the contents of the buffer (see the optional built-in module `struct` for a way to decode C structures encoded as strings).

`listen` (backlog)
  Listen for connections made to the socket. The backlog argument specifies the maximum number of queued connections and should be at least 1; the maximum value is system-dependent (usually 5).

`makefile` ([mode[, bufsize]])
  Return a file object associated with the socket. (File objects are described in , ``File Objects.'') The file object references a `dup()`ped version of the socket file descriptor, so the file object and socket object may be closed or garbage-collected independently. The optional mode and bufsize arguments are interpreted the same way as by the built-in `open()` function.

`recv` (bufsize[, flags])
  Receive data from the socket. The return value is a string representing the data received. The maximum amount of data to be received at once is specified by bufsize. See the Unix manual page recv(2) for the meaning of the optional argument flags; it defaults to zero.

`recvfrom` (bufsize[, flags])
  Receive data from the socket. The return value is a pair `(string, address)` where string is a string representing the data received and address is the address of the socket sending the data. The optional flags argument has the same meaning as for `recv()` above. (The format of address depends on the address family -- see above.)

`send` (string[, flags])
  Send data to the socket. The socket must be connected to a remote socket. The optional flags argument has the same meaning as for `recv()` above. Returns the number of bytes sent.

`sendto` (string[, flags], address)
  Send data to the socket. The socket should not be connected to a remote socket, since the destination socket is specified by address. The optional flags argument has the same meaning as for `recv()` above. Return the number of bytes sent. (The format of address depends on the address family -- see above.)

`setblocking` (flag)
  Set blocking or non-blocking mode of the socket: if flag is 0, the socket is set to non-blocking, else to blocking mode. Initially all sockets are in blocking mode. In non-blocking mode, if a `recv()` call doesn't find any data, or if a `send()` call can't immediately dispose of the data, a `error` exception is raised; in blocking mode, the calls block until they can proceed.

`setsockopt` (level, optname, value)
  Set the value of the given socket option (see the Unix manual page setsockopt(2)). The needed symbolic constants are defined in the `socket` module (`SO_*` etc.). The value can be an integer or a string representing a buffer. In the latter case it is up to the caller to ensure that the string contains the proper bits (see the optional built-in module `struct` for a way to encode C structures as strings).

`shutdown` (how)
  Shut down one or both halves of the connection. If how is `0`, further receives are disallowed. If how is `1`, further sends are disallowed. If how is `2`, further sends and receives are disallowed.

Note that there are no methods `read()` or `write()`; use `recv()` and `send()` without flags argument instead.