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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 SUNOS
in.echod
in.echod(1M) System Administration Commands in.echod(1M) NAME
in.echod - UDP or TCP echo protocol service daemon SYNOPSIS
in.echod FMRI svc:/internet/echo:default DESCRIPTION
FMRI stands for Fault Management Resource Identifier. It is used to identify resources managed by the Fault Manager. See fmd(1M) and smf(5). The in.echod service provides the server-side of the echo protocol. This protocol is used for debugging and bandwidth measurement and is available on both TCP and UDP transports, through port 7. The in.echod service is an inetd(1M) smf(5) delegated service. The in.echod detects which transport is requested by examining the socket it is passed by the inetd daemon. TCP-based service Once a connection is established, the in.echod echoes any data received from the client back to the client. The server echoes data until the client program terminates the connection. UDP-based service The in.echod listens for UDP datagrams. When a datagram is received, the server creates a UDP datagram containing the data it received and sends it to the client. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNW | +-----------------------------+-----------------------------+ |Interface Stability |Evolving | +-----------------------------+-----------------------------+ SEE ALSO
inetd(1M), attributes(5), smf(5) RFC 862 SunOS 5.10 23 Aug 2004 in.echod(1M)