ØMQ Manual - ØMQ/4.2.0


zmq_ipc - ØMQ local inter-process communication transport


The inter-process transport passes messages between local processes using a system-dependent IPC mechanism.

The inter-process transport is currently only implemented on operating systems that provide UNIX domain sockets.


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 inter-process transport, the transport is ipc, and the meaning of the address part is defined below.

Binding a socket

When binding a socket to a local address using zmq_bind() with the ipc transport, the endpoint shall be interpreted as an arbitrary string identifying the pathname to create. The pathname must be unique within the operating system namespace used by the ipc implementation, and must fulfill any restrictions placed by the operating system on the format and length of a pathname.

When the address is wild-card *, zmq_bind() shall generate a unique temporary pathname. The caller should retrieve this pathname using the ZMQ_LAST_ENDPOINT socket option. See zmq_getsockopt(3) for details.

any existing binding to the same endpoint shall be overridden. That is, if a second process binds to an endpoint already bound by a process, this will succeed and the first process will lose its binding. In this behaviour, the ipc transport is not consistent with the tcp or inproc transports.

the endpoint pathname must be writable by the process. When the endpoint starts with /, e.g., ipc:///pathname, this will be an absolute pathname. If the endpoint specifies a directory that does not exist, the bind shall fail.

on Linux only, when the endpoint pathname starts with @, the abstract namespace shall be used. The abstract namespace is independent of the filesystem and if a process attempts to bind an endpoint already bound by a process, it will fail. See unix(7) for details.

IPC pathnames have a maximum size that depends on the operating system. On Linux, the maximum is 113 characters including the "ipc://" prefix (107 characters for the real path name).

Unbinding wild-card address from a socket

When wild-card * endpoint was used in zmq_bind(), the caller should use real endpoint 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 ipc transport, the endpoint shall be interpreted as an arbitrary string identifying the pathname to connect to. The pathname must have been previously created within the operating system namespace by assigning it to a socket with zmq_bind().


Assigning a local address to a socket

//  Assign the pathname "/tmp/feeds/0"
rc = zmq_bind(socket, "ipc:///tmp/feeds/0"); assert (rc == 0);

Connecting a socket

//  Connect to the pathname "/tmp/feeds/0"
rc = zmq_connect(socket, "ipc:///tmp/feeds/0"); assert (rc == 0);

See also

zmq_bind(3) zmq_connect(3) zmq_inproc(7) zmq_tcp(7) zmq_pgm(7) zmq_vmci(7) zmq_getsockopt(3) zmq(7)


This page was written by the ØMQ community. To make a change please read the ØMQ Contribution Policy at