Home > Articles > Web Development

Learn Socket Programming with Python

Programming expert Jesse Smith shows you how to use Python to program socket applications. You will learn about the various socket types and how to apply them.
Like this article? We recommend

As a web developer, I haven't had the need to do much socket programming because a web application framework takes care of those details for me. However, there has been a time or two when knowing socket programming was useful in terms of providing secure data transfer to other in-house servers from over the web.

It's hard to avoid socket programming altogether because virtually every type of server needs it to host different types of server applications. If you're a Windows programmer, you probably know socket programming quite well.

Python makes socket programming easy. Other languages—such as Java or C#—make this more complicated by having to use numerous streaming and buffer methods. Using these methods can get confusing because you are often making compound method calls to do something conceptually simple.

With Python, you do not have to worry because these details are taken care of for you. As you will see, Python socket programming is rather elegant.

Socket Programming in General

Sockets use protocols to determine the connection type used to do port-to-port communication between client and server machines. There are protocols for IP addressing, Dynamic Name Servers (DNS), email, FTP, and so on. Each of these server types uses different protocol definitions to transfer data. There are two types of socket connections: stateful and stateless (or connectionless) connections.

With stateful connections, the protocol requires an acknowledgement from the target machine that the data did indeed get there and that all the data is intact. The Terminal Control Protocol is a stateful protocol because it needs packet routing confirmations between source and destination ports.

Services that require that the data be sent and acknowledged often use the TCP protocol as the basis for their specific protocol. For example, the Simple Mail Transfer Protocol (SMTP) for sending email is a TCP-based protocol. It is important to know that an email got to where it was meant to go. 

Stateless connections do not require data transfer acknowledgement like TCP does. A commonly used stateless protocol is the Universal Datagram Protocol (UDP). A DNS service uses this protocol as the basis for packet routing. UDP is often used for larger data packet routing and extends the UDP protocol to include more information about packet routing.

Python Socket Programming

Python has a socket method that allows you to set up virtually any type of socket. To set up a TCP socket, use the following code:

	from socket import *
	tcpSock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

The first parameter is the socket family type, and in this case it happens to be an Internet socket. There are also different types of socket families (Unix, Internet, etc.). The second parameter tells the Python interpreter that this is a streaming socket. Streaming sockets are stateful socket connections.

To set up a UDP socket, do the following:

udpSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

In this example, the socket family type is still Internet, but the socket packet type has changed to Datagram, which informs the interpreter that this is a UDP socket.

After a socket is defined, there are several methods that you can use to manage connections. To demonstrate, code for a simple TCP timestamp server appears here:

from socket import *
from time import ctime
HOST = 'localhost'
PORT = 28812
BUFSIZE = 1024
ADDR = (HOST, PORT)

tcpTimeSrvrSock = socket(AF_INET,SOCK_STREAM)
tcpTimeSrvrSock.bind(ADDR)
tcpTimeSrvrSock.listen(50)

while True:
  print 'waiting for connection...'
  tcpTimeClientSock, addr = tcpTimeSrvrSock.accept()
  print '...connected from:', addr

  while True:
    data = tcpTimeClientSock.recv(BUFSIZE)
    if not data:
      break
    tcpTimeClientSock.send('[%s] %s' % (ctime(), data))
    
  tcpTimeClientSock.close()
tcpTimeSrvrSock.close() 

In this example, the local machine is used to set up the connection. After the address is defined, containing the host and port, the address is then bound to the socket controller. The socket is set to listen to up to 50 connections maximum. The while loop keeps the socket active, waiting for connections in a thread-like context. The connection is set up to read 1024 bytes at a time from the incoming data stream.

Reading chunks of data at a time is often referred to as chunking. Data chunking allows the server to process incoming data more effectively. For large streams, processing a stream all at once can result in very poor server performance. In the last part of this example, the server sends back the client's message with a timestamp using the Python format specifier.

To use the server, there has to be a client application that connects to it. You can easily build socket clients that send data to the server.

An example client socket program appears follows:

from socket import *
HOST = 'localhost'
PORT = 28812
BUFSIZE = 1024
ADDR = (HOST, PORT)
tcpTimeClientSock = socket(AF_INET, SOCK_STREAM)
tcpTimeClientSock.connect(ADDR)
while True:
  data = raw_input('> ')
  if not data:
      break
  tcpTimeClientSock.send(data)
  data = tcpTimeClientSock.recv(BUFSIZE)
  if not data:
      break
print data
tcpTimeClientSock.close()

Notice a lot of this code is the same as the server code, but this time we are creating an active input message loop instead of setting up a listener. Once prompted for the input message, the user types in the message, and the server sends the message back with the timestamp prepended to the message.

The examples thus far use only the general socket methods. If you were going to do protocol-specific implementations (i.e. SMTP), these protocol types come with their own additional methods.

Conclusion

In this article you learned about Python's basic socket programming functionality. You can easily set up a TCP server and client using the general socket methods of the Python standard library.

Sending messages back and forth using different basic protocols is quite simple. Python also has a higher-level module called socketserver. With socketserver, you can set up mail servers and clients.

In the next article, I will cover this module in more depth while giving examples of client and server to demonstrate the most common methods, as was done here.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020