Opening a Server-Side Socket for Receiving Data

sSock = socket(AF_INET, SOCK_STREAM) sSock.bind((serverHost, serverPort)) sSock.listen(3) conn, addr = sSock.accept() data = conn.recv(1024)

The socket module included with Python provides a generic interface to a variety of low-level socket programming. This phrase discusses how to implement a low-level socket server using the socket module.

The first step in implementing a server-side socket interface is to create the server socket by calling -socket(family, type [, proto]), which creates and returns a new socket. family refers to the address family listed in Table 7.1, type refers to the socket types listed in Table 7.2, and proto refers to the protocol number, which is typically omitted except when working with raw sockets.

Table 7.1. Protocol Families for Python Sockets

Family	Description
AF_INET	Ipv4 protocols (TCP, UDP)
AF_INET6	Ipv6 protocols (TCP, UDP)
AF_UNIX	Unix domain protocols

Table 7.2. Socket Types for Python Sockets

Type	Description
SOCK_STREAM	Opens an existing file for reading.
SOCK_DGRAM	Opens a file for writing. If the file already exists, the contents are deleted. If the file does not already exist, a new one is created.
SOCK_RAW	Opens an existing file for updating, keeping the existing contents intact.
SOCK_RDM	Opens a file for both reading and writing. The existing contents are kept intact.
SOCK_SEQPACKET	Opens a file for both writing and reading. The existing contents are deleted.

Once the socket has been created, it must be bound to an address and port using the bind(address) method, where address refers to a tuple in the form of (hostname, port). If the hostname is an empty string, the server will allow connections on any available Internet interface on the system.

Note

You can specify <broadcast> as the hostname to use the socket to send broadcast messages.

After the socket has been bound to an interface, it can be activated by invoking the listen(backlog) method, where backlog is an integer that indicates how many pending connections the system should queue before rejecting new ones.

Once the socket is active, implement a while loop to wait for client connections using the accept() method. Once a client connection has been accepted, data can be read from the connection using the recv(buffsize [,flags]) method. The send(string [,flags]) method is used to write a response back to the client.

from socket import * serverHost = '' # listen on all interfaces serverPort = 50007 #Open socket to listen on sSock = socket(AF_INET, SOCK_STREAM) sSock.bind((serverHost, serverPort)) sSock.listen(3) #Handle connections while 1: #Accept a connection     conn, addr = sSock.accept()     print 'Client Connection: ', addr     while 1: #Receive data         data = conn.recv(1024)         if not data: break         print 'Server Received: ', data         newData = data.replace('Client', 'Processed') #Send response         conn.send(newData) #Close Connection     conn.close()

server_socket.py

Client Connection:  ('137.65.77.24', 1678) Server Received:  Client Message1 Server Received:  Client Message2

Output from server_socket.py code