Log the client process ID for Windows named pipes too.

Turns out it didn't take much googling to find the right API function.

windows/winhsock.c

@@ -236,6 +236,26 @@ static const char *sk_handle_socket_error(Socket s)
 
 static char *sk_handle_peer_info(Socket s)
 {
+    Handle_Socket ps = (Handle_Socket) s;
+    ULONG pid;
+    static HMODULE kernel32_module;
+    DECL_WINDOWS_FUNCTION(static, BOOL, GetNamedPipeClientProcessId,
+                          (HANDLE, PULONG));
+
+    if (!kernel32_module) {
+        kernel32_module = load_system32_dll("kernel32.dll");
+        GET_WINDOWS_FUNCTION(kernel32_module, GetNamedPipeClientProcessId);
+    }
+
+    /*
+     * Of course, not all handles managed by this module will be
+     * server ends of named pipes, but if they are, then it's useful
+     * to log what we can find out about the client end.
+     */
+    if (p_GetNamedPipeClientProcessId &&
+        p_GetNamedPipeClientProcessId(ps->send_H, &pid))
+        return dupprintf("process id %lu", (unsigned long)pid);
+
     return NULL;
 }