diff --git a/src/channel.c b/src/channel.c
index d57c24f..fc738c5 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -207,7 +207,6 @@
     /*
      * Tell Windows we are interested in receiving message when there
      * is input on the editor connection socket.
-     * TODO: change WM_NETBEANS to something related to the channel index.
      */
     if (channel->ch_inputHandler == -1)
 	channel->ch_inputHandler =
@@ -648,6 +647,24 @@
 #endif
 }
 
+# if defined(FEAT_GUI_W32) || defined(PROTO)
+/*
+ * Lookup the channel index from the socket.
+ * Returns -1 when the socket isn't found.
+ */
+    int
+channel_socket2idx(sock_T fd)
+{
+    int i;
+
+    if (fd >= 0)
+	for (i = 0; i < channel_count; ++i)
+	    if (channels[i].ch_fd == fd)
+		return i;
+    return -1;
+}
+# endif
+
 /*
  * Write "buf" (NUL terminated string) to channel "idx".
  * When "fun" is not NULL an error message might be given.