is sendto and recvfrom thread safe?
Hi,
If I have a global socket file descriptor, can I call sendto and recvfrom on that file descriptor concurrently with out using semaphores around the call to sendto and recvfrom?
What about for TCP sockets?
Thanks
Lee
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Quoted 7 lines · On Thu, 21 Aug 2003 01:06:45 -0500 "Lee Chin" <[email protected]> wrote:
Hi,
If I have a global socket file descriptor, can I call sendto and recvfrom on that file descriptor concurrently with out using semaphores around the call to sendto and recvfrom?What about for TCP sockets?
Thanks
Lee
It depends on your definition of thread safe.
Sendto and recvfrom are for UDP which is a datagram protocol; therefore each call sends and receives a separate data unit. The application protocol has to be atomic to work with UDP anyway. Your application has to deal with out of order, and dropped packets.
If you use TCP sockets with threaded applications you better do application level locking per socket and have enough information in your protocol to describe the length of each operation. TCP is a byte stream, and with multiple threads sending it is possible to "mix the streams". Multiple threads reading will get out of order data.
This is true of all OS's that I know about that support threads (Windows, Solaris, Linux, ...).