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38.17.3 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 keywordvalue 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).