Question

I have a simple application on a OpenWRT style router. It’s written in C++ currently. The router (embedded Linux) has very limited disk space and RAM. For example there is not enough space to install Python.

So, I want to control this daemon app via the network. I have read some tutorials on creating sockets, and listening to the port for activity. But I haven’t been able to integrate the flow into a C++ class. And I haven’t been able to figure out how to decode the information received, or how to send a response.

All the tutorials I’ve read are dead ends, they show you how to make a server that basically just blocks until it receives something, and then returns a message when it got something.

Is there something a little more higher level that can be used for this sort of thing?

Answer 1

Sounds like what you are asking is “how do I build a simple network service that will accept requests from clients and do something in response?” There are a bunch of parts to this — how do you build a service framework, how do you encode and decode the requests, how do you process the requests and how do you tie it all together?

It sounds like you’re having problems with the first and last parts. There are two basic ways of organizing a simple service like this — the thread approach and the event approach.

In the thread approach, you create a thread for each incoming connection. That thread reads the messages (requests) from that connection (file descriptor), processes them, and writes back responses. When a connection goes away, the thread exits. You have a main ‘listening’ thread that accepts incoming connections and creates new threads to handle each one.

In the event approach, each incoming request becomes an event. You then have event handlers that processes these events, sending back responses. Its important that the event handlers NOT block and complete promptly, otherwise the service may appear to lock up. Your program has a main event loop that waits for incoming events (generally blocking on a single poll or select call) and reads and dispatches each event as appropriate.