Linux sockets terminating listening thread

I have a thread that is essentially just for listening on a socket. I have the thread blocking on accept() currently.

How do I tell the thread to finish any current transaction and stop listening, rather than staying blocked on accept?

I don't really want to do non-blo开发者_C百科cking if I don't have to...

Use the select(2) call to check which fd are ready to read.

The file descriptors from call can be read with out it blocking. eg accept() on the returned fd will immediately create a new connection.

Basically you have two options, the first one is to use interrupts: i.e http://www.cs.cf.ac.uk/Dave/C/node32.html (see the signal handler section, it also supply a th_kill example).

From accept man page:

accept() shall fail if:
EINTR
    The system call was interrupted by a signal that was caught before a valid connection arrived. 

Another option is to use Non blocking sockets and select(): i.e.: http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=%2Frzab6%2Frzab6xnonblock.htm

Anyhow, usually in multi-threaded servers there's one thread which accepts new connections and spawns other threads for each connections. Since accept()ing and than recv()ing, can delay new connections requests... (Unless you're working with one client, and then accept()ing and recieving might be OK)

Use pthread_cancel on the thread. You'll need to make sure you've installed appropriate cancellation handlers (pthread_cleanup_push) to avoid resource leaks, and you should disable cancellation except for the duration of the accept call to avoid race conditions where the cancellation request might get acted upon later by a different function than accept.

Note that, due to bugs in glibc's implementation of cancellation, this approach could lead to lost connections and file descriptor leaks. This is because glibc/NPTL provides no guarantee that accept did not already finish execution and allocate a new file descriptor for the new connection before the cancellation request is acted upon. It should be a fairly rare occurrence but it's still an issue to consider...

See: http://sourceware.org/bugzilla/show_bug.cgi?id=12683

and for a discussion of the issue: Implementing cancellable syscalls in userspace

From Wake up thread blocked on accept() call

I just used the shutdown() system call and it seems to work...