Python Socket Programming

Python Socket Programming: Quick Guide for Starters

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The Python programming language is commonly used in the modern world today. According to DZone, there are over 147,000 packages in the Python package repository, which makes it usable for almost everything. Python’s library in the socket programming area includes a variety of built-in modules that play a big part in the inter-process of networking and communication. Networking and sockets have literal volumes written about them as their scope covers large subjects.

If you are new to Python, sockets, or networking, the feeling of being overwhelmed with all these terms is quite normal. This article aims to help you understand more about socket programming in Python.

What Is Socket Programming?

Socket programming is the process of connecting two nodes to communicate with each other on a network. The first socket, also called a node, listens to a specific port on an IP while the second socket gains communication as it reaches out to look for connections. In this case, the server conforms the listener socket while the client communicates with the server. Socket programming is activated by importing the socket library to make a basic socket.

This type of programming provides a form of inter-process communication (IPC) where the main elements consist of basically a server and a client. Serving its purpose to be the backbones of web browsing, this inter-process communication is used in any network that can either be logical or physical. Logical network refers to the connection between a local network connected to a device or a computer. On the other hand, physical network refers to the connection between an external network connected to other networks.

What Is a Socket?

Communication between machines has become much more efficient with the combination of sockets and the Internet Networking (INET). Sockets and the collection of sockets, called socket API, are used to send and receive messages across a network. A socket is determined by its port number and IP address, which is why these elements should be thoroughly configured to establish a connection. It is an end-point of a two-way communication link where it is possible to listen to incoming messages and send acknowledgements to both ends of the environment. Sockets are the most prevalent form of inter-process communication as the server-client environment works well with networks, especially in a cross-platform transmission.

What Is a Socket Module?

There are two levels, low and high, in which network access is available. The socket module refers to the ways in which server and client machines can transmit at hardware level with the use of socket endpoints on the brink of the operating system. In correlation, the socket API fortifies network protocols that are either connectionless or connection-oriented.

Socket Function

The socket.socket() function included in the socket module is necessary to create a socket object. The general syntax of importing this function is:

s = socket.socket (socket_family, socket_type, protocol=0)

The socket function has different types of arguments including:

  1. socket_family – is the domain which is AF_INET by default. AF_INET6, AF_UNIX, AF_CAN or AF_RDS are other acceptable values.
  2. socket_type – is the type of communication between two end points, normally SOCK_STREAM by default for connection-oriented protocol (TCP). The SOCK_DGRAM value is implemented for connection-less protocol (UDP).
  3. protocol — is usually with 0 value as default. This is used to determine a variant of a protocol within a family and type.

Server Socket

The socket within a server is called a server socket. Its socket object has several methods available for the server functionality:

  1. s.bind() – is the method that binds the specified IP address and port number to the socket (hostname, port number pair).
  2. s.listen() – is the method that initiates the server to start TCP listener into looping which continuously tries to look for a connection request from the client.
  3. s.accept() – is the method that accepts TCP client connection passively while identifying the client socket and its address when a connection arrives.

Client Socket

The socket set up on the client’s end is called a client socket. Its socket object mainly uses the connect() method to send connection requests to the server socket.

  1. connect() – is the method that initiates a TCP server connection and takes two arguments, the IP address and port number of the server, to send or receive data from both ends of the two sockets.

General Socket

The general socket methods are useful in socket programming other than the mentioned client and server methods.

  1. s.recv() – is the method that receives TCP message sent to the client. For the server socket, it uses a remote socket with an accepted request: client.recv(bytes). For the client socket, it uses: obj.recv(bytes).
  2. s.send() – is the method that transmits a TCP message to the client. For the server socket, it uses the address it has confronted with: client.send(bytes). For the client socket, it sends data to the socket it has acknowledged a connection with: obj.send(bytes).
  3. s.recvfrom() – is the method that receives the UDP message in the case of UDP protocol.
  4. s.sendto() – is the method that transmits UDP message and is to be used only in the case of UDP protocol.
  5. s.sendall() – is the method similar to send(). This method, however, sends data from bytes continuously until the entire data has been sent or an error intercepted.
  6. s.close() – is the method that closes the socket
  7. socket.gethostname() – is the method used to return the hostname.

For a more detailed Python socket programming tutorial, watch this video:

The Socket Library of Python

The Python socket library contains an outstanding foundation for networking support in both low and high levels. These two levels of network service access in Python are applied depending on the network’s module. Programmers can access the basic socket service for operating systems using Python’s library with low-level support. This level is accommodated by modules such as SSL, asyncore, and asynchat. In low-level support, programmers can administer both connection-oriented and connection-less protocols for programming with the network’s servers and clients.

Furthermore, programmers can access application-level network protocols using Python’s library with high-level support. This level is accommodated by modules such as HTTP, URLLIB, and FTP. In high-level support, programmers have access to the functionality of socket modules that are authorized to obtain the socket interface.

Sockets may be executed on different channel types such as TCP, UDP, etc. The socket library consists of specific divisions for managing common transports and generic interface.

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