best way to write a linux daemon [closed]

Question

For work i need to write a tcp daemon to respond to our client software and was wondering if any one had any tips on the best way to go about this.

Should i fork for every new connection as normally i would use threads?

Answer 1

It depends on your application. Threads and forking can both be perfectly valid approaches, as well as the third option of a single-threaded event-driven model. If you can explain a bit more about exactly what you're writing, it would help when giving advice.

For what it's worth, here are a few general guidelines:

• If you have no shared state, use forking.
• If you have shared state, use threads or an event-driven system.
• If you need high performance under very large numbers of connections, avoid forking as it has higher overhead (particularly memory use). Instead, use threads, an event loop, or several event loop threads (typically one per CPU).

Generally forking will be the easiest to implement, as you can essentially ignore all other connections once you fork; threads the next hardest due to the additional synchronization requirements; the event loop more difficult due to the need to turn your processing into a state machine; and multiple threads running event loops the most difficult of them all (due to combining other factors).

Answer 2

I'd suggest forking for connections over threads any day. The problem with threads is the shared memory space, and how easy it is to manipulate the memory of another thread. With forked processes, any communication between the processes has to be intentionally done by you.

Just searched and found this SO answer: What is the purpose of fork?. You obviously know the answer to that, but the #1 answer in that thread has good points on the advantages of fork().