Start better error reporting for sockets

tests/standalone/src/io/EchoServerTest.dart

Index: tests/standalone/src/io/EchoServerTest.dart
diff --git a/tests/standalone/src/io/EchoServerTest.dart b/tests/standalone/src/io/EchoServerTest.dart
index 428d3d7e0db5fe425b7ca0326f90bb7ea271c744..b0c77bf6d07e379a456a75e7441785b30d023eca 100644
--- a/tests/standalone/src/io/EchoServerTest.dart
+++ b/tests/standalone/src/io/EchoServerTest.dart
@@ -75,8 +75,8 @@ class EchoServerGame {
       handleRead();
     }
 
-    void errorHandler() {
-      Expect.fail("Socket error");
+    void errorHandler(Exception e) {
+      Expect.fail("Socket error $e");
     }
 
     void connectHandler() {
@@ -183,8 +183,8 @@ class EchoServer extends TestingServer {
       connection.close();
     }
 
-    void errorHandler() {
-      Expect.fail("Socket error");
+    void errorHandler(Exception e) {
+      Expect.fail("Socket error $e");
     }
 
     connection.onData = messageHandler;