Ubuntu Manpage: nng_ws - WebSocket transport

NAME

       nng_ws - WebSocket transport

SYNOPSIS

           #include <nng/transport/websocket/ws.h>

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

DESCRIPTION

The ws transport provides communication support between peers across a TCP/IP network
using WebSockets <https://tools.ietf.org/html/rfc6455>. Both IPv4 and IPv6 are supported
when the underlying platform also supports it.

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

Registration
Depending upon how the library was built, it may be necessary to register the transport by
calling nng_ws_register().

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.

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.

A URI may be restricted to IPv6 using the scheme ws6:// or wss6://, and may be restricted
to IPv4 using the scheme ws4:// or wss4://.

Note
Specifying ws6:// or wss6:// may not prevent IPv4 hosts from being used with
IPv4-in-IPv6 addresses, particularly when using a wildcard hostname with listeners.
The details of this varies across operating systems.

Note
The ws4:// , ws6://, wss4:// and wss6:// schemes are specific to NNG, and might not be
understood by other implementations.

Tip
We recommend using either numeric IP addresses, or names that are specific to either
IPv4 or IPv6 to prevent confusion and surprises.

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
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).

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
(string) Concatenation 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
(string) Concatenation of multiple lines terminated by CRLF sequences, that can be
used to add further headers to the HTTP response sent when connecting. This option can
be set on listeners, and retrieved from pipes.

NNG_OPT_WS_RECV_TEXT
(bool) Enable receiving of TEXT frames at the WebSocket layer. This option should only
be used with the low level nng_stream API. When set, the stream will accept in-bound
TEXT frames as well as BINARY frames.

Note
The SP protocols (such as REQ) require BINARY frames as they pass binary protocol
data. Hence this option should not be used with such protocols.

Note
RFC 6455 requires that TEXT frames be discarded and the connection closed if the frame
does not contain valid UTF-8 data. NNG does not perform any such validation.
Applications that need to be strictly conformant should check for this themselves.

NNG_OPT_WS_SEND_TEXT
(bool) Enable sending of TEXT frames at the WebSocket layer. This option should only
be used with the low level nng_stream API. When set, the stream will send TEXT frames
instead of BINARY frames.

Note
NNG does not check the frame data, and will attempt to send whatever the client
requests. Peers that are compliant with RFC 6455 will discard TEXT frames (and break
the connection) if they do not contain valid UTF-8.

NNG_OPT_TLS_CONFIG
(nng_tls_config *) The underlying TLS configuration object for wss:// endpoints. A
hold is placed on the underlying configuration object before returning it. The caller
should release the object with nng_tls_config_free() when it no longer needs the TLS
configuration.

Tip
Use this option when advanced TLS configuration is required.

NNG_OPT_TLS_CA_FILE
(string) Write-only option naming a file containing certificates to use for peer
validation. See nng_tls_config_ca_file() for more information.

NNG_OPT_TLS_CERT_KEY_FILE
(string) Write-only option naming a file containing the local certificate and
associated private key. The private key used must be unencrypted. See
nng_tls_config_own_cert() for more information.

NNG_OPT_TLS_AUTH_MODE
(int) Write-only option used to configure the authentication mode used. See
nng_tls_config_auth_mode() for more details.

NNG_OPT_TLS_VERIFIED
(bool) Whether the remote peer has been properly verified using TLS authentication.
May return incorrect results if peer authentication is disabled.

NNG_OPT_TLS_PEER_CN
(string) This read-only option returns the common name of the peer certificate. May
return incorrect results if peer authentication is disabled.

NNG_OPT_TLS_PEER_ALT_NAMES
(string list) returns string list with the subject alternative names of the peer
certificate. May return incorrect results if peer authentication is disabled.

NAME

SYNOPSIS

DESCRIPTION

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