37.17.3 Testing Availability of Network Features

To test for the availability of a given network feature, use featurep like this:

     (featurep 'make-network-process '(keyword value))

The result of the first form is t if it works to specify keyword with value value in make-network-process. The result of the second form is t if keyword is supported by make-network-process. Here are some of the keyword—value pairs you can test in this way.

(:nowait t)

Non-nil if non-blocking connect is supported.

(:type datagram)

Non-nil if datagrams are supported.

(:family local)

Non-nil if local (a.k.a. “UNIX domain”) sockets are supported.

(:family ipv6)

Non-nil if IPv6 is supported.

(:service t)

Non-nil if the system can select the port for a server.

To test for the availability of a given network option, use featurep like this:

     (featurep 'make-network-process 'keyword)

Here are some of the options you can test in this way.

:bindtodevice

:broadcast

:dontroute

:keepalive

:linger

:oobinline

:priority

:reuseaddr

That particular network option is supported by make-network-process and set-network-process-option.