结合服务器和客户端python套接字

Question

I am attempting to make a local network chat program using python (which may later be in c), and TCP sockets.

My intent is to have the server listen on the current computer's address for incoming messages, and relay these to the client (how I am not sure yet). The client will be a simple gui which can send messages to active servers on local connections. In effect this setup will form something of a node network.

Is it possible to have both the server and client in the same application, preferably without using threads? I know the server will pause while listening for a connection, so the gui cannot respond.

If I cannot have both in the same application I was thinking of having 2 applications which communicate to each other, however threads seem like a better alterative as I'll be using 2 processes either way. If I was to have separate apps how could I send strings to the client from server, to update the gui?

Can I make some sort of event (on the client side) which occurs when the wants server sends a message to client?

In addition, how could I check if a server is active (available and bound to its computer address, awaiting a message) ?

Is my server/client relationship model reasonable? Any suggestions?

I have checked similar socket questions on stack overflow, but haven't found any which specifically address my issue. I may have missed some, so please redirect my attention to them if they are found relevant.

This question seems very similar: Python socket server: listening to multiple clients , however they do not seem to have a 'server' & client for each.

Note: I am new to sockets & networking.

Answer 1

1. First of all, you need to read some good book or some articles (google it - there are tons of them) about socket programming. Stackoverflow is not enough. You will just waste your time trying to learn something from random questions-answers.
2. "Server" doesn't mean "receiving only mode" and "client" doesn't mean "sending only mode. There is full duplex connection between client and server. The difference is "server" will open a port and will wait for incoming connection. And "client" knowing server address will start this connection. Once the connection is established - "client" and "server" will be able to communicate full duplex.
3. Yes it is possible to "have both the server and client in the same application". But it is rare behavior. You will need it on the server side if your server will need to for example make requests to some other servers (to google.com for example). To do this you'll just need to handle both types of sockets: active and passive.
4. "how could I check if a server is active?". If the server is "ON" you will be able to connect to it. If not - your attempt will return an error (an exception in Python). That's it.
5. There are two methods to use sockets: blocking mode and nonblocking mode. In the latter case, your program does not need to wait for the end of the operation. It can do their business at the same time of receiving or sending data through the socket.
6. I not recommend you use raw sockets. It's not rational. Raw sockets are needed only if you are trying to create some brand-new sockets framework with some unique features (but in order to do this you should be an expert in sockets development). Just because there are already are tens of already existing frameworks only in Python (and some for a C/C++. libevent is one of the best of them). One of Python async socket libraries is asyncio - the part of the Python standard library (for modern Python versions).

Good luck!