It makes possible to run several instances of the full software stack on the same machine and perform locally functional testing of complex network configurations. As socket_wrapper redirects all communications, happening via IPv4/IPv6 sockets and emulate those using traditional unix domain sockets, when we pass a file descriptor we also need to pass additional information with socket_wrapper. Multichannel support has been implemented using fd-passing in Samba and to be able to test this as part of the Samba testsuite, we need to have support for it in socket_wrapper.