diff -r fe01c4c7931a -r 5c0a5c30cda8 src/Pure/System/system_channel.scala
--- a/src/Pure/System/system_channel.scala	Sun Feb 14 12:50:46 2016 +0100
+++ b/src/Pure/System/system_channel.scala	Sun Feb 14 13:11:19 2016 +0100
@@ -20,7 +20,8 @@
 {
   private val server = new ServerSocket(0, 2, InetAddress.getByName("127.0.0.1"))
 
-  def server_name: String = "127.0.0.1:" + server.getLocalPort
+  val server_name: String = "127.0.0.1:" + server.getLocalPort
+  override def toString: String = server_name
 
   def rendezvous(): (OutputStream, InputStream) =
   {