Butler stream servers can generate client address.

logdog/client/cmd/logdog_butler/subcommand_serve.go

Index: logdog/client/cmd/logdog_butler/subcommand_serve.go
diff --git a/logdog/client/cmd/logdog_butler/subcommand_serve.go b/logdog/client/cmd/logdog_butler/subcommand_serve.go
index c2c586072aeaf30cad8e408fa370e23ec56244ac..b6fdf519047cba599fbbd6697e66e5f962a1827e 100644
--- a/logdog/client/cmd/logdog_butler/subcommand_serve.go
+++ b/logdog/client/cmd/logdog_butler/subcommand_serve.go
@@ -40,7 +40,11 @@ func (cmd *serveCommandRun) Run(app subcommands.Application, args []string, _ su
 		}.Errorf(a, "Invalid stream server URI.")
 		return configErrorReturnCode
 	}
-	streamServer := createStreamServer(a, cmd.uri)
+	streamServer, err := createStreamServer(a, cmd.uri)
+	if err != nil {
+		log.WithError(err).Errorf(a, "Failed to create stream server.")
+		return runtimeErrorReturnCode
+	}
 
 	if err := streamServer.Listen(); err != nil {
 		log.Errorf(log.SetError(a, err), "Failed to connect to stream server.")