I have a single non-blocking socket sending udp packets to multiple targets and receiving responses from all of them on the same socket. I'm reading in a dedicated thread but writes (sendto) can come from several different threads.
Is this a safe without any additional synchronization? Do I need to write while holding a mutex? Or, do writes need to come from the same thread and I need a queue?
The kernel will synchronize access to underlying file descriptor for you, so you don't need a separate mutex. There would be a problem with this approach if you were using TCP, but since we are talking about UDP this should be safe, though not necessarily best way.
sendto()s from different threads race, but you should ensure that sendto() doesn't race with close().You can write to the socket from a single or multiple threads. If you write to a socket from multiple threads, they should be synchronized with a mutex. If instead your threads place their messages in a queue and a single thread pulls from the queue to do the writes, reads and writes to/from the queue should be protected by a mutex.
Reading and writing to the same socket from different threads won't interfere with each other.
