40.17.3 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 this form is t if it works to specify keyword with value value in 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)

The accepted keyword values are :bindtodevice, etc. For the complete list, see Network Options. This form returns non-nil if that particular network option is supported by make-network-process (or set-network-process-option).