nng_tcp(7)
==========
:doctype: manpage
:manmanual: nng
:mansource: nng
:icons: font
:source-highlighter: pygments
:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
            This software is supplied under the terms of the MIT License, a \
            copy of which should be located in the distribution where this \
            file was obtained (LICENSE.txt).  A copy of the license may also \
            be found online at https://opensource.org/licenses/MIT.

NAME
----
nng_tcp - TCP/IP transport for nng

SYNOPSIS
--------

[source,c]
----------
#include <nng/transport/tcp/tcp.h>

int nng_tcp_register(void);
----------

DESCRIPTION
-----------

The _nng_tcp_ transport provides communication support between
_nng_ sockets across a TCP/IP network.  Both IPv4 and IPv6
are supported when the underlying platform also supports it.

// We need to insert a reference to the nanomsg RFC.

Registration
~~~~~~~~~~~~

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

URI Format
~~~~~~~~~~

This transport uses URIs using the scheme `tcp://`, followed by
an IP address or hostname, followed by a colon and finally a
TCP port number.  For example, to contact port 80 on the localhost
either of the following URIs could be used: `tcp://127.0.0.1:80` or
`tcp://localhost:80`.

When specifying IPv6 addresses, the address must be enclosed in
square brackets (`[]`) to avoid confusion with the final colon
separating the port.

For example, the same port 80 on the IPv6 loopback address ('::1') would
be specified as `tcp://[::1]:80`.

NOTE: When using symbolic names, the name is resolved when the
name is first used. _nng_ won't become aware of changes in the
name resolution until restart,
usually.footnote:[This is a bug and will likely be fixed in the future.]

The special value of 0 (`INADDR_ANY`) can be used for a listener
to indicate that it should listen on all interfaces on the host.
A short-hand for this form is to either omit the address, or specify
the asterisk (`*`) character.  For example, the following three
URIs are all equivalent, and could be used to listen to port 9999
on the host:

  1. `tcp://0.0.0.0:9999`
  2. `tcp://*:9999`
  3. `tcp://:9999`

The entire URI must be less than `NNG_MAXADDRLEN` bytes long.

Socket Address
~~~~~~~~~~~~~~

When using an `nng_sockaddr` structure, the actual structure is either
of type `nng_sockaddr_in` (for IPv4) or `nng_sockaddr_in6` (for IPv6).
These are `struct` types with the following definitions:

[source,c]
--------
#define NNG_AF_INET    3 <1>
#define NNG_AF_INET6   4
#define NNG_MAXADDRLEN 128

typedef struct {
    // ... <2>
    uint16_t sa_family;                 // must be NNG_AF_INET
    uint16_t sa_port;                   // TCP port number
    uint32_t sa_addr;
    // ...
} nng_sockaddr_in;

typedef struct {
    // ... <2>
    uint16_t sa_family;                 // must be NNG_AF_INET6
    uint16_t sa_port;                   // TCP port number
    uint8_t  sa_addr[16];
    // ...
} nng_sockaddr_in6;
--------
<1> The values of these macros may change, so applications
should avoid depending upon their values and instead use them symbolically.
<2> Other members may be present, but only those listed here
are suitable for application use.

The `sa_family` member will have the value `NNG_AF_INET` or `NNG_AF_INET6`.
The `sa_port` and `sa_addr` are the TCP port number and address, both in
network byte order (most significant byte is first).

Transport Options
~~~~~~~~~~~~~~~~~

The _tcp_ transport has no special
options.footnote:[Options for TCP keepalive, linger, and nodelay are planned.]
 
AUTHORS
-------
link:mailto:garrett@damore.org[Garrett D'Amore]

SEE ALSO
--------
<<nng.adoc#,nng(7)>>

COPYRIGHT
---------

Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]

This document is supplied under the terms of the
https://opensource.org/licenses/LICENSE.txt[MIT License].
