= nng_ws(7)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document 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_ws - WebSocket transport for nng

== SYNOPSIS

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

int nng_ws_register(void);
int nng_wss_register(void);
----------

== DESCRIPTION

The _nng_ws_ transport provides communication support between
_nng_ sockets across a TCP/IP network using 
https://tools.ietf.org/html/rfc6455[WebSockets].  Both IPv4 and IPv6
are supported when the underlying platform also supports it.

The protocol details are documented in
http://nanomsg.org/rfcs/sp-websocket-v1.html[WebSocket Mapping for Scalability Protocols].

=== Registration

Depending upon how the library was built, it may be necessary to
register the transport by calling `nng_ws_register`.  This function
returns zero on success, or an nng error value if the transport
cannot be initialized for any reason.

If TLS support is enabled in the library, secure WebSockets (over TLS v1.2) 
can be used as well, but the secure transport may have to be registered using
the `nng_wss_register` function.  (Note that this function will not be
present if TLS support was not enabled in the library.)

=== URI Format

This transport uses URIs using the scheme `ws://`, followed by
an IP address or hostname, optionally followed by a colon and an
TCP port number, optionally followed by a path.  (If no port number
is specified then port 80 is assumed.  If no path is specified then
a path of `/` is assumed.)
For example, the URI `ws://localhost/app/pubsub` would use
port 80 on localhost, with the path `/app/pubsub`.

Secure WebSockets (if enabled) use the scheme `wss://`, and the default
TCP port number of 443.  Otherwise the format is the same as for regular
WebSockets.

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 path and port on the IPv6 loopback address (`::1`)
would be specified as `ws://[::1]/app/pubsub`.

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.]

NOTE: The value specified as the host, if any, will also be used
in the `Host:` HTTP header during HTTP negotiation.

To listen to all ports on the system, the host name may be elided from
the URL on the listener.  This will wind up listening to all interfaces
on the system, with possible caveats for IPv4 and IPv6 depending on what
the underlying system supports.  (On most modern systems it will map to the
special IPv6 address `::`, and both IPv4 and IPv6 connections will be
permitted, with IPv4 addresses mapped to IPv6 addresses.)

=== 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).

=== Server Instances

This transport makes use of shared HTTP server instances, permitting multiple
sockets or listeners to be configured with the same hostname and port. When
creating a new listener, it is registered with an existing HTTP server instance
if one can be found.  Note that the matching algorithm is somewhat simple,
using only a string based hostname or IP address and port to match.  Therefore
it is recommended to use only IP addresses or the empty string as the hostname
in listener URLs.

Likewise, when sharing a server instance, it may not be possible to alter
TLS configuration if the server is already running, as there is only a single
TLS configuration context for the entire server instance.

All sharing of server instances is only typically possible within the same
process.

The server may also be used by other things (for example to serve static
content), in the same process.

=== Transport Options

The following transport options are available. Note that
setting these must be done before the transport is started.

NOTE: The TLS specific options (beginning with `NNG_OPT_TLS_`) are
only available for `wss://` endpoints.

`NNG_OPT_WS_REQUEST_HEADERS`::

This value is a string, consisting of multiple lines terminated
by CRLF sequences, that can be used to add further headers to the
HTTP request sent when connecting.  This option can be set on dialers,
and retrieved from pipes.

`NNG_OPT_WS_RESPONSE_HEADERS`::

This value is a string, consisting of multiple lines terminated
by CRLF sequences, that can be used to add furthe headers to the
HTTP response sent when connecting.  This option can be set on listeners,
and retrieved from pipes.

`NNG_OPT_TLS_CONFIG`::

This option is used on an endpoint to access the underlying TLS
configuration object.  The value is of type `nng_tls_config *`.

TIP: Use this option when advanced TLS configuration is required.

`NNG_OPT_TLS_CA_FILE`::

This is a write-only option used to load certificates associated
associated private key from a file.
See <<nng_tls_config_ca_file#,nng_tls_config_ca_file(3)>> for more
information.

`NNG_OPT_TLS_CERT_KEY_FILE`::

This is a write-only option used to load the local certificate and
associated private key from a file. The private key used must be
unencrypted. (Use the `NNG_OPT_TLS_CONFIG` option to access the underlying
TLS configuration if more advanced configuration is needed.)
See <<nng_tls_config_own_cert#,nng_tls_config_own_cert(3)>> for more
information.

`NNG_OPT_TLS_AUTH_MODE`::

This is a write-only option used to configure the authentication mode
used.  It can take an integer with value `NNG_TLS_AUTH_MODE_NONE`,
`NNG_TLS_AUTH_MODE_REQUIRED`, or `NNG_TLS_AUTH_MODE_OPTIONAL`.  See
<<nng_tls_config_auth_mode#,nng_tls_config_auth_mode(3)>> for more details.

`NNG_OPT_TLS_VERIFIED`::

This is a read-only option which returns a boolean value (integer 0 or 1).
It will true (1) if the remote peer has been properly verified using TLS
authentication, or false (0) otherwise.  This option may return incorrect
results if peer authentication is disabled with `NNG_TLS_AUTH_MODE_NONE`.

// We should also look at a hook mechanism for listeners. Probably this could
// look like NNG_OPT_WS_LISTEN_HOOK_FUNC which would take a function pointer
// along the lines of int hook(void *, char *req_headers, char **res_headers),
// and NNG_OPT_LISTEN_HOOK_ARG that passes the void * passed in as first arg.
// Alternatively we can uplevel the HTTP API and pass the actual HTTP objects.

== SEE ALSO

<<nng#,nng(7)>>,
<<nng_tls_config_alloc#,nng_tls_config_alloc(3)>>
