Building a Web Client in Python

In order to access the Internet, we need to create a socket. The syntax for this call is as follows:

<variable> = socket.socket(<family>, <type>) </blockquote>

The recognised socket families are:

• AF_INET: IPv4 protocols (both TCP and UDP)
• AF_INET6: IPv6 protocols (both TCP and UDP)
• AF_UNIX: UNIX domain protocols

The first two are obviously internet protocols. Anything that travels over the internet can be accessed in these families. Many networks still do not run on IPv6. So, unless you know otherwise, it is safest to default to IPv4 and use AF_INET.

The socket type refers to the type of communication used through the socket. The five socket types are as follows:

• SOCK_STREAM: a connection-oriented, TCP byte stream
• SOCK_DGRAM: UDP transferral of datagrams (self-contained IP packets that do not rely on client-server confirmation)
• SOCK_RAW: a raw socket
• SOCK_RDM: for reliable datagrams
• SOCK_SEQPACKET: sequential transfer of records over a connection

By far, the most common types are SOCK_STEAM and SOCK_DGRAM because they function on the two protocols of the IP suite. The latter three are much rarer and so may not always be supported.

Let's therefore create a socket and assign it to variable; here I use c (for connection). [blockquote shade=yes] c = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

Index: Building a Web Client in Python

1. Network Programming is not Voodoo
2. Programming Networks in Python: the Basics
3. Importing Modules for Network Programming in Python
4. Giving Python the Internet Protocol Information
5. Creating a Socket With Python
6. Connecting Sockets With Python
7. Python Asks the Web Server for the File
8. Printing the Web Page With Python
9. The Python Code for a Simple Web Client Program