SYNOPSIS
#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 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. 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.
| 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.[1] |
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:
#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.
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 *.
| 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(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_CONFIGoption to access the underlying TLS configuration if more advanced configuration is needed.) See 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, orNNG_TLS_AUTH_MODE_OPTIONAL. See 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.