Sockets with Python Intro

Sockets are used in networking. The idea of a socket is to aid in the communication between two entities. When you view a website, you are opening a port and connecting to that website via sockets. In this, you are the client, and the website is the server. Quite literally, you are served data.

A natural point of confusion here is the difference between sockets and ports. You can think of a port much like a shipping port, where boats dock at the port and unload goods. Then, you can think of the ship itself as the socket. The ocean is the internet. Much like shipping ports, a socket (our ship in this metaphor), is bound by a specific port. Docking at a different port is not allowed, for ships or sockets!

Now, let's go ahead and play with ports and sockets in Python! This can be a slightly confusing topic, so I will do my best to document everything. The video should help as well if you are finding yourself confused.

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print(s)
		

Generally, we use sockets to communicate between a couple of places, so let's show an example of that. One of the most common transmissions of data is between a "client" and "server," most often in the case of a user visiting a website and being served web-content, much like you are being served this page right now. Sockets did that for you.

server = 'reddit.com'

port = 80

server_ip = socket.gethostbyname(server)
print(server_ip)
		

Here is some more information on open ports and hacking: Open Ports and Hacking

So, above, we were able to access reddit.com via port 80. From there, we were able to determine the server's IP address by using gethostbyname().

Now, let's make a request, making sure it is in-line with what the port will find acceptable from our socket:

request = "GET / HTTP/1.1\nHost: "+server+"\n\n"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("reddit.com", 80))
	  

Above, we defined our request as an HTTP request, where we wanted to "GET" data from the "Host" of PythonProgramming.net

Next, we defined our socket in the same manner as we had before.

Finally, we make our connection to PythonProgramming.net on port 80. This is just a connection. We have defined out request, but not actually made any request, so let's make the request:

s.send(request.encode())
result = s.recv(4096)

print(result)
		

import this

Since I said the buffer was almost a waste, I should probably show how to make the output actually buffer as well. Here's how:

Instead of using print(result), comment or delete that, then do:

while (len(result) > 0):
    print(result)
    result = s.recv(4096)
	  

If you wanted to do this with an HTTPS forcing website, such as PythonProgramming.net, you would instead do something like:

import socket
import ssl

context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
context.verify_mode = ssl.CERT_REQUIRED
context.check_hostname = True
context.load_default_certs()

server = "pythonprogramming.net"
port = 443
server_ip = socket.gethostbyname(server)

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s = context.wrap_socket(s, server_hostname=server)

request = "GET / HTTP/1.1\nHost: "+server+"\n\n"

s.connect((server,port))
s.send(request.encode())
result = s.recv(4096)

while (len(result) > 0):
    print(result)
    result = s.recv(4096)

The next tutorial: Simple Port Scanner with Sockets