public async Task TestRpcFromServerToClient()
        {
            int result = 0;
            var t1     = Run(async() =>
            {
                await _server.ConnectAsync(5000);
                _server.Start();
                result = int.Parse((await _server.CallAsync("test", 5))[0].ToString());
            });
            var t2 = Run(async() =>
            {
                await _client.ConnectAsync(5000);
                _client.Register("test", (arg) =>
                {
                    return(new object[] { int.Parse(arg[0].ToString()) + 1 });
                });
                _client.Start();
            });
            await Task.WhenAll(t1, t2);

            Assert.AreEqual(6, result);
        }