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Unable to create a UDP client from thread?
Post 302481760 by sehang on Sunday 19th of December 2010 09:42:40 PM
12-19-2010
Quote:
Hi,
The answer from fpmurphy is short, but up to the point. Let me explain a little bit; In a multi-threaded process, a signal handler process-wide, that is global to all threads. However, when the signal is delivered, the system library / kernel picks up a particular thread that shall run the handler. This might be any thread in the process.
In your particular example, you wish that the handler runs in the context of thread1, so that the recvfrom() gets interrupted. But, unless you force it too, the handler may run in the context of the main thread. In that case, nothing will happen. This is likely what you are experiencing.
The way to force the handler to run in the context of thread1 (or equivalently, we say the signal to be delivered to thread1) is using pthread_sigmask() as mentioned by fpmurphy. Please refer to example in the link provided above, to see how it works. Incidentally, this example was my first contribution to the SUSv3 standard; so if you have questions please feel free to ask
And finally, I would suggest to resort other strategies than alarm() & co. to implement a timeout on the receive operation if you're multi-threaded.
Cheers, Loïc.
The answer from fpmurphy is short, but up to the point. Let me explain a little bit; In a multi-threaded process, a signal handler process-wide, that is global to all threads. However, when the signal is delivered, the system library / kernel picks up a particular thread that shall run the handler. This might be any thread in the process.
In your particular example, you wish that the handler runs in the context of thread1, so that the recvfrom() gets interrupted. But, unless you force it too, the handler may run in the context of the main thread. In that case, nothing will happen. This is likely what you are experiencing.
The way to force the handler to run in the context of thread1 (or equivalently, we say the signal to be delivered to thread1) is using pthread_sigmask() as mentioned by fpmurphy. Please refer to example in the link provided above, to see how it works. Incidentally, this example was my first contribution to the SUSv3 standard; so if you have questions please feel free to ask
And finally, I would suggest to resort other strategies than alarm() & co. to implement a timeout on the receive operation if you're multi-threaded.
Cheers, Loïc.
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LEARN ABOUT DEBIAN
jack.udp
JACK.UDP(1) JACK.UDP(1) NAME
jack.udp - JACK UDP Transport Client SYNOPSIS
jack.udp [options] send|recv OPTIONS
-b : Set the ring buffer size in frames (default=4096). -c : Set the client name (default=jack.udp-PID). -n : Set the number of channels, and therefore the number of JACK ports (default=2). -p : Set the port number (default=57160). -r : The remote host name, for use in send mode (default="127.0.0.1"). DESCRIPTION
jack.udp is a UDP audio transport mechansim for JACK. The send mode reads signals from a set of JACK input ports and sends UDP packets to the indicated port at the indicated host at a rate determined by the local JACK daemon. The recv mode reads incoming packets at the indi- cated port and writes the incoming data to a set of JACK output ports at a rate that is determined by the local JACK daemon. This transport mechanism is unreliable. Both send and recv clients will report buffer overflow and underflow occurences, and recv clients will report dropped and out-of-order packets, and shutdown on channel mismatch packets. In practice this mechanism can be made highly reli- able over local networks. jack.udp implements no connection logic, use jack.plumbing(1) instead. EXAMPLE
192.0.0.1:~$ jack.udp -r 192.0.0.2 send 192.0.0.2:~$ jack.udp recv AUTHOR
Rohan Drape http://slavepianos.org/rd/ SEE ALSO
jackd(1) AUTHOR
Rohan Drape <rd@slavepianos.org> Author. 01/10/2012 JACK.UDP(1)