This documentation is for the TIP (development tree) of NNG and may represent unreleased changes or functionality that is experimental, and is subject to change before release. The latest released version is v1.3.2. See the documentation for v1.3.2 for the most up-to-date information.



nng_ipc - IPC transport


#include <nng/transport/ipc/ipc.h>

int nng_ipc_register(void);


(transport, ipc) The ipc transport provides communication support between sockets within different processes on the same host. For POSIX platforms, this is implemented using UNIX domain sockets. For Windows, this is implemented using Windows Named Pipes. Other platforms may have different implementation strategies.


This transport is generally built-in to the core, so no extra steps to use it should be necessary.

URI Formats

Traditional Names

(URI, ipc://) This transport uses URIs using the scheme ipc://, followed by a path name in the file system where the socket or named pipe should be created.

On Windows, all names are prefixed by \\.\pipe\ and do not reside in the normal file system. On POSIX platforms, the path is taken literally, and is relative to the current directory, unless it begins with /, in which case it is relative to the root directory.
When using relative paths on POSIX systems, the address used and returned in properties like NNG_OPT_LOCADDR and NNG_OPT_URL will also be relative. Consequently, they will only be interpreted the same by processes that have the same working directory. To ensure maximum portability and safety, absolute paths are recommended whenever possible.
If compatibility with legacy nanomsg applications is required, then path names must not be longer than 122 bytes, including the final NUL byte. This is because legacy versions of nanomsg cannot express URLs longer than 128 bytes, including the ipc:// prefix.

UNIX Aliases

(URI, unix://) The unix:// scheme is an alias for ipc:// and can be used inter-changeably, but only on POSIX systems.

The purpose of this scheme is to support a future transport making use of AF_UNIX on Windows systems, at which time it will be necessary to discriminate between the Named Pipes and the AF_UNIX based transports.

Abstract Names

(URI, abstract://) On Linux, this transport also can support abstract sockets. Abstract sockets use a URI-encoded name after the scheme, which allows arbitrary values to be conveyed in the path, including embedded NUL bytes. For example, the name "a\0b" would be represented as abstract://a%00b.

An empty name may be used with a listener to request “auto bind” be used to select a name. In this case the system will allocate a free name. The name assigned may be retrieved using NNG_OPT_LOCADDR.
NNG cannot represent an abstract socket with the empty name.
Abstract names do not include the leading NUL byte used in the low-level socket address.

Abstract sockets do not have any representation in the file system, and are automatically freed by the system when no longer in use. Abstract sockets ignore socket permissions, but it is still possible to determine the credentials of the peer with NNG_OPT_PEER_UID, etc.

Socket Address

When using an nng_sockaddr structure, the actual structure is of type nng_sockaddr_ipc, except for abstract sockets, which use nng_sockaddr_abstract.

Transport Options

The following transport options are supported by this transport, where supported by the underlying platform.