TCP Transport

DESCRIPTION

The tcp transport provides communication support between sockets within different processes using the TCP stream protocol over IP or IPv6.

URI Formats

This transport uses URIs using the scheme tcp://, followed by an IP address or hostname, and port number, formatted as follows.

For host names and IPv4 literal addresses, the hostname or IP address is followed by a colon, and then a TCP port number. For example, tcp://myservice.net:123 would refer to a server available at myservice.net on TCP port 123.

For IPv6 literal addresses, the IPv6 address must be enclosed in square brackets, then the colon and finally the TCP port. For example, tcp://[::1]:7890 would refer to a service running on the IPv6 loopback (::1) on TCP port 7890.

Forcing IPv4 or IPv6

To force the selection of either IPv4 or IPv6, the scheme may be specified as either tcp4:// or tcp6:// instead of just tcp://. This should only be needed when a hostname that might resolve either way is supplied instead of an explicit IP address.

Listening to All Addresses

When listening, a zero IP address can be supplied by either eliding the address altogether, or by specifying 0.0.0.0 (IPv4) or :: (IPv6) explicitly. If left empty, IPv6 will be selected if available on the host, otherwise IPv4 will be selected.

Tip

IP addresses may be more reliable than host names. Certainly when using the URL for a listener, it is better to use an IP address that is known to exist on the local system, or the zero address to listen to all interfaces.

Socket Address

When using an nng_sockaddr, the concrete type is either nng_sockaddr_in or nng_sockaddr_in6, depending on whether IPv4 or IPv6 is in use.

Transport Options

The following transport options are supported by this transport, where supported by the underlying platform.