Python Sockets - SOCK_STREAM and SOCK_DGRAM
There are two type of sockets:
SOCK_DGRAM. Below we have a comparison of both types of sockets.
|For TCP protocols||For UDP protocols|
|Reliable delivery||Unrelible delivery|
|Guaranteed correct ordering of packets||No order guaranteed|
|Connection-oriented||No notion of connection(UDP)|
Socket Module in Python
To create a socket, we must use
socket.socket() function available in the Python socket module, which has the general syntax as follows:
S = socket.socket(socket_family, socket_type, protocol=0)
- socket_family: This is either
AF_INET. We are only going to talk about INET sockets in this tutorial, as they account for at least 99% of the sockets in use.
- socket_type: This is either
- Protocol: This is usually left out, defaulting to
Now, if you remember we have discussed client-server socket program in the last tutorial as well. Now let's dig deeper into that program and try to understand the terms and methods used.
Client Socket Methods
Following are some client socket methods:
To connect to a remote socket at an address. An address format(host, port) pair is used for
AF_INET address family.
Server Socket Methods
Following are some server socket methods:
This method binds the socket to an address. The format of address depends on socket family mentioned above(
This method listens for the connection made to the socket. The backlog is the maximum number of queued connections that must be listened before rejecting the connection.
This method is used to 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 which can be used to send and receive data on that connection, and address is the address bound to the socket on the other end of the connection.
For detailed view of methods refer documentation: https://docs.python.org/2/library/socket.html
Few General Socket Methods
For the below defined socket object,
s = socket.socket(socket_family, socket_type, protocol=0)
|TCP Socket Methods||UDP Socket Methods|
s.recv()→ Receives TCP messages
s.recvfrom()→ Receives UDP messages
s.send()→ Transmits TCP messages
s.sendto()→ Transmits UDP messages
Some Basic Socket Methods
close() This method is used to close the socket connection.
gethostname() This method returns a string containing the hostname of the machine where the python interpreter is currently executing. For example: localhost.
gethostbyname() If you want to know the current machine's IP address, you may use