SYNOPSIS

TCP is an ubiquitous, reliable, unicast transport. When connecting distributed applications over a network with ØMQ, using the TCP transport will likely be your first choice.

ADDRESSING

A ØMQ endpoint is a string consisting of a transport:// followed by an address. The transport specifies the underlying protocol to use. The address specifies the transport-specific address to connect to.

For the TCP transport, the transport is tcp, and the meaning of the address part is defined below.

Assigning a local address to a socket

When assigning a local address to a socket using zmq_bind() with the tcp transport, the endpoint shall be interpreted as an interface followed by a colon and the TCP port number to use.

An interface may be specified by either of the following:

  • The wild-card *, meaning all available interfaces.

  • The primary IPv4 or IPv6 address assigned to the interface, in its numeric representation.

  • The non-portable interface name as defined by the operating system.

The TCP port number may be specified by:

  • A numeric value, usually above 1024 on POSIX systems.

  • The wild-card *, meaning a system-assigned ephemeral port.

When using ephemeral ports, the caller should retrieve the actual assigned port using the ZMQ_LAST_ENDPOINT socket option. See zmq_getsockopt(3) for details.

Unbinding wild-card addres from a socket

When wild-card * endpoint was used in zmq_bind(), the caller should use real endpoind obtained from the ZMQ_LAST_ENDPOINT socket option to unbind this endpoint from a socket using zmq_unbind().

Connecting a socket

When connecting a socket to a peer address using zmq_connect() with the tcp transport, the endpoint shall be interpreted as a peer address followed by a colon and the TCP port number to use. You can optionally specify a source_endpoint which will be used as the source address for your connection; tcp://source_endpoint;'endpoint', see the interface description above for details.

A peer address may be specified by either of the following:

  • The DNS name of the peer.

  • The IPv4 or IPv6 address of the peer, in its numeric representation.

Note: A description of the ZeroMQ Message Transport Protocol (ZMTP) which is used by the TCP transport can be found at http://rfc.zeromq.org/spec:15

EXAMPLES

Assigning a local address to a socket
//  TCP port 5555 on all available interfaces
rc = zmq_bind(socket, "tcp://*:5555");
assert (rc == 0);
//  TCP port 5555 on the local loop-back interface on all platforms
rc = zmq_bind(socket, "tcp://127.0.0.1:5555");
assert (rc == 0);
//  TCP port 5555 on the first Ethernet network interface on Linux
rc = zmq_bind(socket, "tcp://eth0:5555");
assert (rc == 0);
Connecting a socket
//  Connecting using an IP address
rc = zmq_connect(socket, "tcp://192.168.1.1:5555");
assert (rc == 0);
//  Connecting using a DNS name
rc = zmq_connect(socket, "tcp://server1:5555");
assert (rc == 0);
//  Connecting using a DNS name and bind to eth1
rc = zmq_connect(socket, "tcp://eth1:0;server1:5555");
assert (rc == 0);
//  Connecting using a IP address and bind to an IP address
rc = zmq_connect(socket, "tcp://192.168.1.17:5555;192.168.1.1:5555");
assert (rc == 0);

SEE ALSO

zmq_bind(3) zmq_connect(3) zmq_pgm(7) zmq_ipc(7) zmq_inproc(7) zmq(7)

AUTHORS

This page was written by the ØMQ community. To make a change please read the ØMQ Contribution Policy at http://www.zeromq.org/docs:contributing.