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nng_ws(7)

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 nng sockets across a TCP/IP network using WebSockets. Both IPv4 and IPv6 are supported when the underlying platform also supports it.

The protocol details are documented in 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().

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.

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. (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).

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 further headers to the HTTP response sent when connecting. This option can be set on listeners, and retrieved from pipes.

NNG_OPT_TLS_CONFIG

(opaque) 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

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

NNG_OPT_TLS_CERT_KEY_FILE

(string) 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() for more information.

NNG_OPT_TLS_AUTH_MODE

(int) 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() for more details.

NNG_OPT_TLS_VERIFIED

(bool) This is a read-only option that is true if the remote peer has been properly verified using TLS authentication, or false otherwise. This option may return incorrect results if peer authentication is disabled with NNG_TLS_AUTH_MODE_NONE.