an class="keyword">val</span>&nbsp;inet6_addr_loopback&nbsp;:&nbsp;<span class="constructor">UnixLabels</span>.inet_addr<br>
&nbsp;&nbsp;<span class="keyword">type</span>&nbsp;socket_domain&nbsp;=&nbsp;<span class="constructor">Unix</span>.socket_domain&nbsp;=&nbsp;<span class="constructor">PF_UNIX</span>&nbsp;<span class="keywordsign">|</span>&nbsp;<span class="constructor">PF_INET</span>&nbsp;<span class="keywordsign">|</span>&nbsp;<span class="constructor">PF_INET6</span><br>
&nbsp;&nbsp;<span class="key