Better error-message when bind fails.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index 2d3ba73b3f7d2abe4aee960eae131c8b7fdc8ce1..a8b60c3e0639e56ea88cc2664fc64201015aff0b 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -431,7 +431,13 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
             if (result is OSError) {
               // Keep first error, if present.
               if (error == null) {
-                error = createError(result, "Connection failed", address, port);
+                int errorCode = result.errorCode;
+                if (errorCode != null && socket.isBindError(errorCode)) {
+                  error = createError(result, "Bind failed", sourceAddress);
+                } else {
+                  error =
+                      createError(result, "Connection failed", address, port);
+                }
               }
               connectNext();
             } else {
@@ -1075,6 +1081,7 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
   nativeCreateBindConnect(
       List<int> addr, int port, List<int> sourceAddr)
       native "Socket_CreateBindConnect";
+  bool isBindError(int errorNumber) native "Socket_IsBindError";
   nativeCreateBindListen(List<int> addr, int port, int backlog, bool v6Only,
                          bool shared)
       native "ServerSocket_CreateBindListen";