Butler stream servers can generate client address.

logdog/client/cmd/logdog_butler/main_posix.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 // +build darwin dragonfly freebsd linux netbsd openbsd
 
 package main
 
 import (
         "errors"
@@ skipping 30 matching lines @@
         return value, nil
 }
 
 // Validates that the URI is correct for Windows.
 func (u streamServerURI) Validate() (err error) {
         _, err = u.Parse()
         return
 }
 
 // Create a POSIX (UNIX named pipe) stream server
-func createStreamServer(ctx context.Context, uri streamServerURI) streamserver.StreamServer {
+func createStreamServer(ctx context.Context, uri streamServerURI) (streamserver.StreamServer, error) {
         path, err := uri.Parse()
         if err != nil {
                 panic("Failed to parse stream server URI.")
         }
-        return streamserver.NewNamedPipeServer(ctx, path)
+        return streamserver.NewUNIXDomainSocketServer(ctx, path)
 }