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87 lines
3.0 KiB
Plaintext
87 lines
3.0 KiB
Plaintext
= zmq_recv(3)
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== NAME
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zmq_recv - receive a message part from a socket
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== SYNOPSIS
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*int zmq_recv (void '*socket', void '*buf', size_t 'len', int 'flags');*
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== DESCRIPTION
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The _zmq_recv()_ function shall receive a message from the socket referenced
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by the 'socket' argument and store it in the buffer referenced by the 'buf'
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argument. Any bytes exceeding the length specified by the 'len' argument shall
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be truncated. If there are no messages available on the specified 'socket'
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the _zmq_recv()_ function shall block until the request can be satisfied.
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The 'flags' argument is a combination of the flags defined below: The 'buf'
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argument may be null if len is zero.
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*ZMQ_DONTWAIT*::
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Specifies that the operation should be performed in non-blocking mode. If there
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are no messages available on the specified 'socket', the _zmq_recv()_
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function shall fail with 'errno' set to EAGAIN.
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Multi-part messages
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~~~~~~~~~~~~~~~~~~~
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A 0MQ message is composed of 1 or more message parts. 0MQ ensures atomic
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delivery of messages: peers shall receive either all _message parts_ of a
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message or none at all. The total number of message parts is unlimited except
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by available memory.
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An application that processes multi-part messages must use the _ZMQ_RCVMORE_
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xref:zmq_getsockopt.adoc[zmq_getsockopt] option after calling _zmq_recv()_ to determine if
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there are further parts to receive.
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== RETURN VALUE
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The _zmq_recv()_ function shall return number of bytes in the message
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if successful. Note that the value can exceed the value of the 'len' parameter
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in case the message was truncated. If not successful the function shall return
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`-1` and set 'errno' to one of the values defined below.
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== ERRORS
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*EAGAIN*::
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Either the timeout set via the socket-option ZMQ_RCVTIMEO (see xref:zmq_setsockopt.adoc[zmq_setsockopt])
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has been reached (flag ZMQ_DONTWAIT not set) without being able to read a message
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from the socket or there are no messages available at the moment (flag ZMQ_DONTWAIT set)
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and the operation would block.
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*ENOTSUP*::
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The _zmq_recv()_ operation is not supported by this socket type.
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*EFSM*::
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The _zmq_recv()_ operation cannot be performed on this socket at the moment
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due to the socket not being in the appropriate state. This error may occur with
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socket types that switch between several states, such as ZMQ_REP. See the
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_messaging patterns_ section of xref:zmq_socket.adoc[zmq_socket] for more information.
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*ETERM*::
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The 0MQ 'context' associated with the specified 'socket' was terminated.
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*ENOTSOCK*::
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The provided 'socket' was invalid.
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*EINTR*::
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The operation was interrupted by delivery of a signal before a message was
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available.
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== EXAMPLE
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.Receiving a message from a socket
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----
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char buf [256];
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nbytes = zmq_recv (socket, buf, 256, 0);
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assert (nbytes != -1);
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----
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== SEE ALSO
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xref:zmq_send.adoc[zmq_send]
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xref:zmq_getsockopt.adoc[zmq_getsockopt]
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xref:zmq_setsockopt.adoc[zmq_setsockopt]
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xref:zmq_socket.adoc[zmq_socket]
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xref:zmq.adoc[zmq]
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== AUTHORS
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This page was written by the 0MQ community. To make a change please
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read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.
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