blacklist a port that cannot be bound on WinRBE

test/core/util/port_isolated_runtime_environment.cc

@@ -43,7 +43,7 @@ static int get_random_port_offset() {
 static int s_initial_offset = get_random_port_offset();
 static gpr_atm s_pick_counter = 0;
 
-int grpc_pick_unused_port_or_die(void) {
+static int pick_unused_port_or_die(void) {
   int orig_counter_val =
       static_cast<int>(gpr_atm_full_fetch_add(&s_pick_counter, 1));
   GPR_ASSERT(orig_counter_val < (MAX_PORT - MIN_PORT + 1));
@@ -51,6 +51,18 @@ int grpc_pick_unused_port_or_die(void) {
          (s_initial_offset + orig_counter_val) % (MAX_PORT - MIN_PORT + 1);
 }
 
+int grpc_pick_unused_port_or_die(void) {
+retry:
+  int port = pick_unused_port_or_die();
+  // 5985 cannot be bound on Windows RBE and results in
+  // WSA_ERROR 10013: "An attempt was made to access a socket in a way forbidden
+  // by its access permissions."
+  if (port == 5985) {
+    goto retry;
+  }
+  return port;
+}
+
 void grpc_recycle_unused_port(int port) { (void)port; }
 
 #endif /* GRPC_PORT_ISOLATED_RUNTIME */