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In this video you're going to learn about DCP communication and how to build a DCP server and client

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what the socket module and python.

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Now networking is a very important aspect of device to device communication over the Internet learning

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how to use the socket module which is built in the python standard library gives us a very practical

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skill to code all sorts of things.

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A network socket.

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In this context is actually a process or a way by which we can make computers or devices talk to each

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other.

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Now you can think of a socket as a building block for network tools in Python and to get a deeper understanding

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of networking and Python programming for networking.

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I would recommend to further study the socket module from the Python.

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Official documentation because it comes with numerous methods that give you plenty of freedom to build

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whatever tools you can think of now outside of the socket module.

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There are many Python modules for networking but I consider this one important since it allows us to

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work at a fairly low level.

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All right so our code today is going to be made of two parts.

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So we have a server and a client.

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The server is going to listen or wait for messages while the client is the one sending the messages.

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So we'll start by coding the server and we'll import import not server but import socket which is the

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module that we're using then we'll define the server address.

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So let's say hosts equals socket guest host name.

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Okay.

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Now this method connects to local hosts then will specify a port number we want to listen on.

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So we'll say fourth equals 9 3 3 7.

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Just a random port number.

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Now notice the host the host is going to be a string while the port in this case is an integer.

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And this is all the socket module wants us to specify the address details.

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Okay.

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And then what we'll do is to create a socket object so let's say SOC on their sport equals socket light

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socket.

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And we're going to use socket f address family iiNet Internet and the type of socket is going to be

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socket SOC under sports or soft underscored stream.

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So this is for DCP communication.

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Things like I said here f underscore iiNet is the address family for IP V for and soc underscore stream

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specifies that we're going for a DCP connection and there's also SOC underscored that diagram which

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is for you the IP often faster and less reliable.

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Next.

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We've been the socket.

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We've just created to the host and the port variables that we've just defined so we do that with soc

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underscored that then and we're going to say host port.

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And as you can see it's taken as a tuple.

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Now we could be more flexible here by allowing the port than the host to be given in the command line

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and in that case we'd be using this as module and maybe we'll do that and another more advanced class.

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OK so we've got a server defined now we need to actually have that less for incoming connections.

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So we do that with soc underscore that.

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Listen one one here denotes the backlog or the number of unaccepted connections before this server starts

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refusing new connections.

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Now let's also have something printed to the output so we'll say print on a new line server started.

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Dot dot dot and then we'll go to a new line then we need to start accepting connections using the DOT

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accept method.

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So it will say Con a DDR equals SOC underscore dot accept.

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Meaning that we accept connections from the client socket con and it's address a DDR once connection

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is established and then we'll do another print saying connection established with

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and then I'd say string a DDR then we'll send a message back to the client.

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So first let's actually put this message into a variable so we'll say message equals on a new line.

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Thank you for connecting not connection with connecting space and then plus string of a DDR and then

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we're actually going to send this message with a coin that send

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we send the message dot in codes or we need to specify the encoding because we're in Python 3 will encoded

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in ASCII and then close the socket.

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So con on that close.

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OK so when we run the script is going to start listening for connections on Port 9 3 3 7 and whoever

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connects it's going to send the message to and then immediately close the socket.

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We could also run this in a while loop to listen continuously but will not do that here.

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All right.

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Next we'll go to.

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But first let's actually save this and then we'll go to the client and call the decline side of it which

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is relatively easier.

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So we start with importing the socket module and then create a socket.

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So SOC under sport socket that socket exactly the same thing as previously.

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So socket dot.

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Am I not.

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Okay.

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And the type of socket is going to be SOC underscore stream.

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Then we can simply use the Connect method to connect to the server without wasting time defining variables

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for the host and port.

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Like with that in the server dot P Y.

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Again like I said you can code the script such as in a way that it receives these values via the command

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line.

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So anyway in this case will connect to the server using SOC underscored that connect

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and we simply pass on socket dot get post to name.

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OK.

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And then also the port 9 3 3 7 as a tuple.

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So once connection is established we want to be able to receive whatever message the server sends.

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So we define a variable message equals SOC underscore dot e CV V and how many bytes we want to receive

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10 twenty.

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Once that's done we'll close the socket with the SOC underscored our clothes and also print the message

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we got from the server with print and as G the decode.

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Of course ASCII control s and that's it.

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A very basic DCP client server coded in python.

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Now let's actually put it to work.

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So I'm going to open up a command prompt and navigate to desktop where both the client and the server

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are located and we'll start the server with Python server dot P Why says server started and then open

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up a another command prompt put them side by side so that you can actually see how they work

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so the server is listening and I also have to navigate to the desktop here.

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And when I hit Python client thought P Y you're going to see how it connects to the server.

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Send the message and we basically can't see the communication between the two of them.

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So I'm going to hit enter.

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Okay so we have a little error here is coquette.

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So it's over here.

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So they have socket control s then we go back go back over here and then do that one more time.

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And as you can see the connection took place so when the client connected its connection established

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with the IP and then it sent the message and it sent.

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Thank you for connecting.

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Awesome right.

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So this was a pretty basic networking Doc through the socket module.

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Of course you can further expand these codes by for example allowing ongoing lesson on the server side

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using loops by receiving command line arguments by executing commands on the server from the client

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by messaging back and forth between the server and the client like a basic chat application for example

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by encrypting the communication and much much more.

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So it's like I always say the only limit is your imagination.