DragonFly On-Line Manual Pages

NN_RECV(3)                      nanomsg manual                      NN_RECV(3)

NAME
       nn_recv - receive a message

SYNOPSIS
       #include <nanomsg/nn.h>

       int nn_recv (int s, void *buf, size_t len, int flags);

DESCRIPTION
       Receive a message from the socket s and store it in the buffer
       referenced by the buf argument. Any bytes exceeding the length
       specified by the len argument will be truncated.

       Alternatively, nanomsg can allocate the buffer for you. To do so, let
       the buf parameter be a pointer to a void* variable (pointer to pointer)
       to the receive buffer and set the len parameter to NN_MSG. If the call
       is successful the user is responsible for deallocating the message
       using the nn_freemsg(3) function.

       The flags argument is a combination of the flags defined below:

       NN_DONTWAIT
           Specifies that the operation should be performed in non-blocking
           mode. If the message cannot be received straight away, the function
           will fail with errno set to EAGAIN.

RETURN VALUE
       If the function succeeds number of bytes in the message is returned.
       Otherwise, -1 is returned and errno is set to to one of the values
       defined below.

ERRORS
       EBADF
           The provided socket is invalid.

       ENOTSUP
           The operation is not supported by this socket type.

       EFSM
           The operation cannot be performed on this socket at the moment
           because socket is not in the appropriate state. This error may
           occur with socket types that switch between several states.

       EAGAIN
           Non-blocking mode was requested and there's no message to receive
           at the moment.

       EINTR
           The operation was interrupted by delivery of a signal before the
           message was received.

       ETIMEDOUT
           Individual socket types may define their own specific timeouts. If
           such timeout is hit this error will be returned.

       ETERM
           The library is terminating.

EXAMPLES
       Receiving a message into a buffer allocated by the user
           This example code will retrieve a message of either 100 bytes or
           less. If a larger message was sent it will be truncated to 100
           bytes.

           char buf [100];
           nbytes = nn_recv (s, buf, sizeof (buf), 0);

       Receiving a message into a buffer allocated by nanomsg
           The following will get a message from the pipe with a buffer
           allocated by the system. It is large enough to accommodate the
           entire message. This is a good way to get the entire message
           without truncating if the size of the message is unknown. It is the
           user's responsibility to call nn_freemsg(3) after processing the
           message.

           void *buf = NULL;
           nbytes = nn_recv (s, &buf, NN_MSG, 0);

           if (nbytes < 0) {
               /* handle error */
               ...
           }
           else {
               /* process message */
               ...
               nn_freemsg (buf);
           }

       Note that this can be more efficient than manually allocating a buffer
       since it is a zero-copy operation.

SEE ALSO
       nn_send(3) nn_recvmsg(3) nn_socket(3) nanomsg(7)

AUTHORS
       Martin Sustrik <sustrik@250bpm.com[1]>

NOTES
        1. sustrik@250bpm.com
           mailto:sustrik@250bpm.com

nanomsg Unknown                   12/23/2015                        NN_RECV(3)