Erle Robotics Python Networking Gitbook Free

Using TCP Streams like Files

Since TCP supports streams of data, they might have already reminded you of normal files, which also support reading and writing as fundamental operations. Python does a very good job of keeping these concepts separate: file objects can read() and write(), sockets can send() and `recv(), and no kind of object can do both. But sometimes you will want to treat a socket like a normal Python file object—often because you want to pass it into code like that of the many Python modules such as pickle, json, and zlib that can read and write data directly from a file. For this purpose, Python provides a makefile() method on every socket that returns a Python file object that is really calling recv() and send() behind the scenes:

>>> import socket
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>> hasattr(s, 'read')
>>> f = s.makefile()
>>> hasattr(f, 'read')

Sockets, like normal Python files, also have a fileno() method that lets you discover their file descriptor number in case you need to supply it to lower-level calls.