From a154ef69da4e41d3a8ce5a3141fe8f052c7ea853 Mon Sep 17 00:00:00 2001 From: Martin Sustrik Date: Mon, 11 Jul 2011 08:34:20 +0200 Subject: Man pages for send & recv function brought up to date Signed-off-by: Martin Sustrik --- doc/zmq_recvmsg.txt | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 doc/zmq_recvmsg.txt (limited to 'doc/zmq_recvmsg.txt') diff --git a/doc/zmq_recvmsg.txt b/doc/zmq_recvmsg.txt new file mode 100644 index 0000000..640768a --- /dev/null +++ b/doc/zmq_recvmsg.txt @@ -0,0 +1,124 @@ +zmq_recvmsg(3) +============== + + +NAME +---- +zmq_recvmsg - receive a message from a socket + + +SYNOPSIS +-------- +*int zmq_recvmsg (void '*socket', zmq_msg_t '*msg', int 'flags');* + + +DESCRIPTION +----------- +The _zmq_recvmsg()_ function shall receive a message from the socket referenced +by the 'socket' argument and store it in the message referenced by the 'msg' +argument. Any content previously stored in 'msg' shall be properly deallocated. +If there are no messages available on the specified 'socket' the _zmq_recvmsg()_ +function shall block until the request can be satisfied. The 'flags' argument +is a combination of the flags defined below: + +*ZMQ_DONTWAIT*:: +Specifies that the operation should be performed in non-blocking mode. If there +are no messages available on the specified 'socket', the _zmq_recvmsg()_ +function shall fail with 'errno' set to EAGAIN. + + +Multi-part messages +~~~~~~~~~~~~~~~~~~~ +A 0MQ message is composed of 1 or more message parts; each message part is an +independent 'zmq_msg_t' in its own right. 0MQ ensures atomic delivery of +messages; peers shall receive either all _message parts_ of a message or none +at all. + +The total number of message parts is unlimited. + +An application wishing to determine if a message is composed of multiple parts +does so by retrieving the value of the _ZMQ_RCVMORE_ socket option on the +'socket' it is receiving the message from. If there are no message parts to +follow, or if the message is not composed of multiple parts, _ZMQ_RCVMORE_ +shall report a value of zero. Otherwise, _ZMQ_RCVMORE_ shall report a value of +1, indicating that more message parts are to follow. + + +RETURN VALUE +------------ +The _zmq_recvmsg()_ function shall return number of bytes in the message +if successful. Otherwise it shall return `-1` and set 'errno' to one of the +values defined below. + + +ERRORS +------ +*EAGAIN*:: +Non-blocking mode was requested and no messages are available at the moment. +*ENOTSUP*:: +The _zmq_recvmsg()_ operation is not supported by this socket type. +*EFSM*:: +The _zmq_recvmsg()_ operation cannot be performed on this socket at the moment +due to the socket not being in the appropriate state. This error may occur with +socket types that switch between several states, such as ZMQ_REP. See the +_messaging patterns_ section of linkzmq:zmq_socket[3] for more information. +*ETERM*:: +The 0MQ 'context' associated with the specified 'socket' was terminated. +*ENOTSOCK*:: +The provided 'socket' was invalid. +*EINTR*:: +The operation was interrupted by delivery of a signal before a message was +available. +*EFAULT*:: +The message passed to the function was invalid. + + +EXAMPLE +------- +.Receiving a message from a socket +---- +/* Create an empty 0MQ message */ +zmq_msg_t msg; +int rc = zmq_msg_init (&msg); +assert (rc == 0); +/* Block until a message is available to be received from socket */ +rc = zmq_recvmsg (socket, &msg, 0); +assert (rc != -1); +/* Release message */ +zmq_msg_close (&msg); +---- + +.Receiving a multi-part message +---- +int64_t more; +size_t more_size = sizeof more; +do { + /* Create an empty 0MQ message to hold the message part */ + zmq_msg_t part; + int rc = zmq_msg_init (&part); + assert (rc == 0); + /* Block until a message is available to be received from socket */ + rc = zmq_recvmsg (socket, &part, 0); + assert (rc != -1); + /* Determine if more message parts are to follow */ + rc = zmq_getsockopt (socket, ZMQ_RCVMORE, &more, &more_size); + assert (rc == 0); + zmq_msg_close (&part); +} while (more); +---- + + +SEE ALSO +-------- +linkzmq:zmq_recv[3] +linkzmq:zmq_send[3] +linkzmq:zmq_sendmsg[3] +linkzmq:zmq_getsockopt[3] +linkzmq:zmq_socket[7] +linkzmq:zmq[7] + + +AUTHORS +------- +The 0MQ documentation was written by Martin Sustrik and +Martin Lucina . -- cgit v1.2.3