Classes and functions

One class is exported:

class Listener(address=None, family=None, backlog=1)

A wrapper for a bound socket or Windows named pipe which is 'listening' connections.

One function is exported:

Client(address, family=None)

Attempts to set up a connection to the listener which is using address address.

The type of the connection is determined by family argument, but this can generally be omitted since it can usually be inferred from the format of the address.

A Connection object is returned. (See Connection objects.)

Listener Objects

Instances of Listener have the following methods:

__init__(address=None, family=None, backlog=1)

address

The address to be used by the bound socket or named pipe of the listener object.

family

The type of the socket (or named pipe) to use.

This can be one of the strings 'AF_INET' (for a TCP socket), 'AF_UNIX' (for a Unix domain socket) or 'AF_PIPE' (for a Windows named pipe). Of these only the first is guaranteed to be available.

If family is None than the family is inferred from the format of address. If address is also None then a default is chosen. This default is the family which is assumed to be the fastest available.

backlog

If the listener object uses a socket then backlog is passed to the listen() method of the socket once it has been bound.

accept()

Accept a connection on the bound socket or named pipe of the listener object.

Returns a Connection object. (See Connection objects.)

close()

Close the bound socket or named pipe of the listener object.

(Note that this is called automatically when the listener is garbage collected.)

Listener objects have the following read-only properties:

address

The address which is being used by the listener object.

last_accepted

The address from which the last accepted connection came.

If this is unavailable then None is returned.

Connection objects

Connections objects have the following methods:

recv()

Return an object sent from the other end of the connection.

send(obj)

Send an object to the other end of the connection.

The object must be picklable.

recv_string()

Return a string sent from the other end of the connection.

send_string(obj)

Send a string to the other end of the connection.

close()

Close the connection.

This is called automatically when the connection is garbage collected.

Address formats

• An 'AF_INET' address is a tuple of the form (hostname, port) where hostname is a string and port is an integer

• An 'AF_UNIX' address is a string representing a filename on the filesystem.

• An 'AF_PIPE' address is a string of the form r'\.pipePipeName'.

  To use Client to connect to a named pipe on a remote computer called ServerName one should use an address of the form r'\ServerNamepipePipeName' instead.

Example

The following server code creates a listener, waits for a connection, receives an object and then sends it back boxed inside a list:

from processing.connection import Listener

address = ('localhost', 6000)     # family is deduced to be 'AF_INET'
listener = Listener(address)

conn = listener.accept()
print 'connection accepted from', listener.last_accepted

obj = conn.recv()
boxed_obj = [obj]
conn.send(boxed_obj)

The following code connects to the server, sends it the number 42, and then prints the reply from the server:

from processing.connection import Client

address = ('localhost', 6000)
conn = Client(address)

obj = 42
print 'sending:', obj
conn.send(obj)
print 'recieved:', conn.recv()    # prints '[42]'