.TH zmq_socket 3 "" "(c)2007-2009 FastMQ Inc." "0MQ User Manuals"
.SH NAME
zmq_socket \- creates 0MQ socket
.SH SYNOPSIS
.B void *zmq_socket (void *context, int type);
.SH DESCRIPTION
Open a socket within the specified
.IR context .
To create a context, use
.IR zmq_init
function.
.IR type
argument can be one of the values defined below. Note that each socket is owned
by exactly one thread (the one that it was created from) and should not be used
from any other thread.

.IP "\fBZMQ_P2P\fP"
Socket to communicate with a single peer. Allows for only a single connect or a
single bind. There's no message routing or message filtering involved.

Compatible peer sockets: ZMQ_P2P.

.IP "\fBZMQ_PUB\fP"
Socket to distribute data. Recv fuction is not implemented for this socket
type. Messages are distributed in fanout fashion to all the peers.

Compatible peer sockets: ZMQ_SUB.

.IP "\fBZMQ_SUB\fP"
Socket to subscribe for data. Send function is not implemented for this
socket type. Initially, socket is subscribed for no messages. Use ZMQ_SUBSCRIBE
option to specify which messages to subscribe for.

Compatible peer sockets: ZMQ_PUB.

.IP "\fBZMQ_REQ\fP"
Socket to send requests and receive replies. Requests are load-balanced among
all the peers. This socket type allows only an alternated sequence of
send's and recv's.

Compatible peer sockets: ZMQ_REP, ZMQ_XREP.

.IP "\fBZMQ_REP\fP"
Socket to receive requests and send replies. This socket type allows
only an alternated sequence of recv's and send's. Each send is routed to
the peer that issued the last received request.

Compatible peer sockets: ZMQ_REQ, ZMQ_XREQ.

.IP "\fBZMQ_XREQ\fP"
Special socket type to be used in request/reply middleboxes such as
.BR zmq_queue(7) .
Requests forwarded using this socket type should be tagged by a proper postix
identifying the original requester. Replies received by this socket are tagged
with a proper postfix that can be use to route the reply back to the original
requester.

Compatible peer sockets: ZMQ_REP, ZMQ_XREP.

.IP "\fBZMQ_XREP\fP"
Special socket type to be used in request/reply middleboxes such as
.BR zmq_queue(7) .
Requests received using this socket are already properly tagged with postfix
identifying the original requester. When sending a reply via XREP socket the
message should be tagged with a postfix from a corresponding request.

Compatible peer sockets: ZMQ_REQ, ZMQ_XREQ.

.IP "\fBZMQ_UPSTREAM\fP"
Socket to receive messages from up the stream. Messages are fair-queued
from among all the connected peers. Send function is not implemented for
this socket type.

Compatible peer sockets: ZMQ_DOWNSTREAM.

.IP "\fBZMQ_DOWNSTREAM\fP"
Socket to send messages down stream. Messages are load-balanced among all the
connected peers. Send function is not implemented for this socket type.

Compatible peer sockets: ZMQ_UPSTREAM.

.SH RETURN VALUE
Function returns socket handle is successful. Otherwise it returns NULL and
sets errno to one of the values below.
.SH ERRORS
.IP "\fBEINVAL\fP"
invalid socket type.
.IP "\fBEMTHREAD\fP"
the number of application threads allowed to own 0MQ sockets was exceeded. See
.IR app_threads
parameter to
.IR zmq_init
function.
.SH EXAMPLE
.nf
void *s = zmq_socket (context, ZMQ_PUB);
assert (s);
int rc = zmq_bind (s, "tcp://192.168.0.1:5555");
assert (rc == 0);
.fi
.SH SEE ALSO
.BR zmq_init (3)
.BR zmq_setsockopt (3)
.BR zmq_bind (3)
.BR zmq_connect (3)
.BR zmq_send (3)
.BR zmq_flush (3)
.BR zmq_recv (3)
.SH AUTHOR
Martin Sustrik <sustrik at 250bpm dot com>