How to Make a TCP IP Server or Client in Python

hello and welcome back to the channel in today's video I'm going to show you how to use Python to act as a TCP IP server or [Music] client so I'm going to go through this code with you line by line and talk a little bit about tcpip protocol along the way basically an Internet Protocol for messaging between devices where there is a client server relationship the server is really the active component and the client is kind of the passive component that's an oversimplification but hopefully that's enough of an explanation that we can start talking about this project this sort of concept definitely sort of straddles between the realm of like the It world and the programmer world and in my case like an automation engineer World um but we're going to go through line by line we're going to start by taking a look at how to set up a TCP IP server script in Python and then we'll take a look at how to set up a TCP IP uh client script and then we'll actually look at how running those two at the same time can connect even on one machine okay so let's get started by uh creating a simple TCP IP server all right and so the uh module really the only module we need to do this sort of thing in Python is called socket so we want to import the socket and then we actually want to create 8 atcp IP socket so we imported the module called socket that has the functionality to allow us to uh create a tcpip socket but we haven't done anything with it yet and so what we'll do is we will say sock equals socket the module and then dot socket the uh uh command within the socket module and then these two parameters in here um socket. ainet and then socket. sock stream this is where um I'm going to be perfectly honest I'm not a network expert these are the parameters I've always used to get this working and so these are the parameters I always put in here and it's worked thus far um I promise if you want to dig a level deeper into the socket modules documentation you can get a better explanation of what each of those are doing um but then we want to bind the socket to the specific port for the server okay so um the way port for the server the way tcpip connections work is the server has an IP address and a port that both the client and the server need to know about and then the client is kind of choosing any open port on its side when it connects if that makes sense so the port only has to be hardcoded for the client in the server to listen to as it relates reles to the server let's keep programming I think it'll make more sense when you um see it written out but so we'll go ahead and we'll say that the server address is equal to and in this case I want it to run right on this machine um so I'm going to say Local Host you could also throw the IP address of your computer in here instead of Local Host so my computer's like 192168 1.64 or something right now I could put that there instead I'm going to say Local Host and then I'm going to um just throw Port 10,000 on there they're all I'm also going to spell address correctly there are something like 62,000 ports that you can use um so just pick a memorable one um I'm going to use 10,000 and then let's print a command something that is very smart to do when you're dealing with like networking and stuff that could kind of go wrong at any moment is give yourself a lot of print statement and so what we'll say is we're starting up uh on and then we'll use two variables in this uh and then we'll say what uh connection the server address has so this will tell us the host IP address and the port that we're using um and this sort of uh format for passing in um variables into a formatted string is a little bit different than I honestly typically use I usually use formatted strings and then curly brackets um but I'm not going to lie there's some really good stack Overflow uh code that I was able to use as the source of a lot of this and they did their prints this way so I'm doing them this way so all we've done thus far really is we've binded bound the server address which is the uh IP address or the host and then the port and we've bound it to the socket instance that we created then we need to listen for inbound connections and then we want to just use sock. listen and then one you could do five you could mess with the variables in there um sock. listen one is good enough for rock and roll so then what we want to do is we want to wait for a connection and we just want to keep uh listening really so the server um does pass data outbound but it's also just wall true we want to wait for a connection because there's not necessarily a guarantee when you have a server that there'll be any clients pulling from it so we want to um basically just wait for a connection to come in all right but then what we'll do is we'll say print waiting for connection and then we will say connection and the client address are the two things that we're going to pull back down from sock. except so another command within the socket module is sock. accept which is basically us saying okay when something hits our server we're going to accept it and we're going to keep track of who's connected to us in this connection and client address variable then what we'll try is we will print connection from and then we will say the client address so this will be a little print statement telling us who's connected to us and as you'll see when we set up the client pie in the second half of this tutorial you'll see uh exactly where that comes from and what it looks like so what we want to do is we want to receive receive man that's a tricky one to spell receive the data in chunks of bytes um and so to do that what we want to say is while true again so now we have tried to uh connect and if we've got a client address then what we're going to do is we're going to say okay the data is equal to whatever we're receiving connection. receive from that port and uh this is where you define how many bytes the buffer size you want to pull in in one message um I've seen this be like 16 bytes I've seen it be quite a bit larger so this um is supposed to be specific is to the size of the messaging that you'll be receiving but in any case you can make it a really large V value because uh at worst case you'll receive everything that's in there so then we'll say we've received and then percent s here and then what we'll do is we'll pass in all of the data that we received Okay so we've got this going on and now what we're going to do is we're going to say if there's data so if in fact we have received anything over that connection then what I want to do is I want to send it back to the client so that way we can show the uh data to and from uh tcpip using like an echo listener client uh server relationship so sending data back to client um and what we're going to have at this point is a bytes object so it's going to look like a string if you were to just print it out which we do up here it's going to look like a string but it's technically bytes and so what we want to do if we want to be able to manip manipulate it like a string we want to do string of data um and then we can start adding stuff to the message so let's say that I want to send it back as whatever the original message was and then I want to say plus extra from the server so in the world of programming if all the client was sending to the server was Hello World then this might be Hello World Plus extra from the server and then going back to um bytes format because that is how we send messages over tcpip so I know we're moving kind of fast but um if you have any questions about the specifics that you see during this tutorial let me know in the comments below because there is a lot to cover and I don't want it to be like a crazy long tutorial um so what we're doing here is we are taking all of the data that we get from the client we are adding a little bit of text to indicate that the server did read it and is sending it back then we're converting it back to bytes using this encoding protocol called utf8 it's a method of encoding strings into bytes and then we send it back over the same connection now because we had an if we want an else and if we don't get any data we want to print no more data from and then the client address so this is just a way of saying hey we're pretty sure we've read everything that was available there so we'll do connection. close to um clean this code up and then we'll do a break and that should Escape our while loop and then because we have a try up top we can throw a finally down here and we'll just say clean up the connection and I'm sorry I think I misspoke earlier connection. close this is where we want connection. close in our finally code we do not need it here although strictly speaking I don't think it would hurt anything there um and all of the code that you're seeing here for both the server and the client will be in a GitHub um Linked In the description of this video as well so if you'd like to not have to follow along line by line it will all be linked below as well so you can go and grab it directly um but what we have done here to Spark Notes speed run through it we imported the socket module we created an instance of a socket stored it in this variable stock we defined our server address which for our application will be this machine and Port 10,000 and then we bind the server address to our socket item and then we are listening for inbound connections when we get a connection we store it in this connection comma client addresses those two variables we display who's connected to us and then we start receiving data and when we receive data over the port through tcpip uh if we get data we add a little bit of text onto it to basically say hey we got this and then pass it back to the client by encoding it as bytes and then when there's no more data be to be processed we close it um but it will return to the outer while loop which will continue waiting for a connection because the nature of a server is you don't necessarily want it to close every time you close a connection with a client if that makes sense so you want the server to keep running even as clients pop onto the network can pop off of the network so let's go ahead and table this right now because if we were to run it right now all you're going to get is okay we're starting up the local host and now we're waiting for a connection because we haven't created the client yet and I don't have a machine um that is a TCP IP client hooked up to my laptop we're not going to hear anything over that connection yet so let's put a pin on this uh the server side and let's write the client side together and then we'll run both of them and we'll talk about what we've built once they're both written all right so now let's go ahead and create a TCP IP socket uh for a client all right and the uh beginning is going to look very quick uh very similar so I'm going to go pretty quick where sock is still equal to socket the module. socket and then still socket do AF inet and socket. sock sock stream there we go and then what we want to do is we want to connect the socket to the port where the server is listening okay so the line is going to look exactly the same server address equals Local Host and then Port 10,000 the reason for this is like we talked about a little bit earlier the client only needs to know the IP address and the uh the port that it needs to use on the server the client assuming your uh TCP IP server does not have like a bunch of security or firewall rules on it the server is the one that has a hard programmed port number and IP address and it's going to receive dat from clients and it's kind of like a surprise what the IP address and the port of the client that are getting used are so the server is the one you have to Define both on the server side and the client side so what we'll do on this side rather than saying um starting up a server we'll say that we are connecting to and then very similar to uh the command we'll say we're connecting to this um address and this port and then we will just pass in the server address server address parameters okay so that'll still give us some useful information in the console window and then we'll do socket. connect to the server address okay and what we'll do now is we will try to send data to the server all right so we want to try to send data and we'll say in this case it'll be a message and it'll just say this is the message uh and then we will say please repeat so we're basically asking the server to read our message and send it back to us and then just so that the print command knows we will say that we are trying to send and then uh variable and then we will say we are trying to send this message and maybe to show that it's a quote we'll do that um print send message I think I missed a space there we go all right and moving on we'll say sock. send all okay so send everything that is in that message but if you remember because that is a string we need to encode our message in utf8 format and turn it into bytes so we can do this just like putting Str before variable makes sure it's a string putting bytes before variable and then an encoding protocol makes sure um that it is a bytes object okay so now we will look for a response back okay and we'll say the amount that we have received starts out as zero and the amount that we expected expected is going to be at least the length of the message okay so we don't necessarily know on the client side if the server is going to be sending anything back or not and these ones are kind of specific for the application I'm setting up here which is an echo client basically saying I'm going to send data I would like you to send the data back more or less just to establish the connection but what we'll say is while the amount that we've received is less than the amount that we expected that means that we want to keep listening so data equals sock. receive and we'll say 1,600 right because that was kind of the max that we uh said we were going to receive on the server side and then what we'll say is okay the amount received just went up by the length of the data that we sent so this is just a track er um more or less keeping track of how much inbound data have we received and we'll print out everything that we've received to show that we got it back on the client side and then data and then we will add just like uh just like in the server side we had a try and a finally we will say in our finally that we are going to print closing socket okay so to give an example of the client whose mission is basically connect to the server to do a specific task or pass a specific piece of data um and then when the work is done it's okay to do sock. close because you're basically saying hey the socket that I was just using until I need to connect to the server again I don't need that connection anymore so I'm just going to go ahead and close it the server's job is to be open and uh constantly kind of listening for connections on that port and the client's job is basically to connect when it needs to connect um and send data went needs to send data okay so uh I know there was a lot in this again I know industrial networking and not even industrial networking really this is just like networking in general um I know this is a little bit different than just straight programming but this is a really important concept especially as you get into communication protocols so let's go ahead and run some tests here I think I can get kind of a crafty view here where we can see our server on the left nope that's also the client here we go we can see our server on the left and we can see our client on the right and I'm going to make the text a little bit smaller um I know if you're watching on like a phone this is probably a lot harder to read but it was big while we were programming so um I'm you know that's half a win so here's the order we're going to do things in we're going to kick on our server right now and in the window you can see we get get all right I've started up on this local host on this port and I'm waiting for a connection now if we did this right when I run the client over here run client so you can see some action in the terminal window of the server it was waiting for a connection oh I got a connection from and then this uh 12701 is really the loopback IP meaning same device but here you can see like this is the IP address and some random Port that the client choose chose to connect to the server and so we say hey we got this message this is the message please repeat so we decide to send data back to the client then we get an empty message there was no more message so the socket closed and now we're waiting for a connection again that's what happened on the server side usually you would use the data that you received to do more than just kick it back to the client as an Echo that's where you would do something useful with the data but for the sake of explaining how to use a TCP server I think we've covered it let's take a look at what the client was doing we were connecting to and it could see Local Host on Port 10,000 then once we were connected we sent this is the message please repeat and then what we got back and you can see these B's in the beginning because we formatted it as bytes so if you want to get rid of that all you have to do is a little bit of like string uh data cleanup but what we got back was this is the message please repeat plus extra from the server so you can see the client sent a message over there and then received back the message as an echo plus the extra message from the server and then we closed the client so what's really cool I have not restarted the server but the client program stopped the script stopped because it sent the message over that it wanted to send so what we can say now is new message please repeat also um and I have not touched the server script it's stayed running the whole time but if I run the client again now you can see the server just said oh it was waiting for a connection it got a new connection and what you can see here is a symptom of how clients work it used a different port this time because the client is just going to grab an open port and then it said oh hey I received new message please repeat also I'm going to send it back and then I had no more data and then the the connection closed and now I'm waiting for a new connection and what happened on the client was I'm sending new message please repeat also and then I received back new message please repeat also plus extra from the server okay so I know that this covered a lot of material and I know that I kept it moving pretty quick again the code will be linked in the GitHub below um and I will get back to you uh on any questions that you have as soon as I can so be sure to drop those in the comments below I thought this was a super interesting concept it came up in my work recently and so I was working on some bigger like Arduino tutorials and physical builds and I was like you know what that was super useful for me and I had a little bit of a hard time finding useful resources on the internet so once I figured it out I figured it would be good subject matter for a video I hope you guys uh enjoyed it be sure to let me know in the comments below what you'd like to see more of on the channel thank you to everyone for continuing to support L Master Tech a massive thank you as always to my patreon supporters good luck with your projects thanks for watching and until next time bye