# Update 9

This week, I focused on the Nethermind codebase for libp2p and raised a PR as well. I worked on the issue [Optimize muxer selection during handshake](https://github.com/NethermindEth/dotnet-libp2p/issues/18).

To enable faster selection, we can pre-select a muxer before the negotiation process, which takes place alongside the handshake. Noise assists with this through its extensions.

Link: [PR](https://github.com/NethermindEth/dotnet-libp2p/pull/90)

In this PR, I’ve also created test functions to validate the connections. Below are the changes I made to the `NoiseProtocol` file:

 if (_extensions.StreamMuxers.Any())
        {
            var selectedProtocol = upChannelFactory?.SubProtocols.FirstOrDefault(proto => proto.Id == _extensions.StreamMuxers[0]);
            context.SpecificProtocolRequest = new ChannelRequest
            {
                SubProtocol = selectedProtocol,
                CompletionSource = context.SpecificProtocolRequest?.CompletionSource
            };
        }

The following test function that I added validates the changes in the code:

  public async Task Test_ConnectionEstablished_With_PreSelectedMuxer()
    {
        IChannel downChannel = new TestChannel();
        IChannel downChannelFromProtocolPov = ((TestChannel)downChannel).Reverse();
        IChannelFactory channelFactory = Substitute.For<IChannelFactory>();
        IPeerContext peerContext = Substitute.For<IPeerContext>();
        IPeerContext listenerContext = Substitute.For<IPeerContext>();
        IProtocol? proto1 = Substitute.For<IProtocol>();
        proto1.Id.Returns("proto1");
        channelFactory.SubProtocols.Returns(new[] { proto1 });
        IChannel upChannel = new TestChannel();
        channelFactory.SubDialAndBind(Arg.Any<IChannel>(), Arg.Any<IPeerContext>(), Arg.Any<IProtocol>())
            .Returns(Task.FromResult(upChannel));
        channelFactory.SubListenAndBind(Arg.Any<IChannel>(), Arg.Any<IPeerContext>(), Arg.Any<IProtocol>())
  .Returns(Task.CompletedTask);
        var multiplexerSettings = new MultiplexerSettings();
        multiplexerSettings.Add(proto1);
        NoiseProtocol proto = new(multiplexerSettings);
        peerContext.LocalPeer.Identity.Returns(new Identity());
        listenerContext.LocalPeer.Identity.Returns(new Identity());
        string peerId = peerContext.LocalPeer.Identity.PeerId.ToString(); // Get the PeerId as a string
        Multiaddress localAddr = $"/ip4/0.0.0.0/tcp/0/p2p/{peerId}";
        peerContext.RemotePeer.Address.Returns(localAddr);
        string listenerPeerId = listenerContext.LocalPeer.Identity.PeerId.ToString();
        Multiaddress listenerAddr = $"/ip4/0.0.0.0/tcp/0/p2p/{listenerPeerId}";
        listenerContext.RemotePeer.Address.Returns(listenerAddr);
        Task ListenTask = proto.ListenAsync(downChannel, channelFactory, listenerContext);
        Task DialTask = proto.DialAsync(downChannelFromProtocolPov, channelFactory, peerContext);
        await DialTask;
        await ListenTask;
        Assert.That(peerContext.SpecificProtocolRequest.SubProtocol, Is.EqualTo(proto1));
        await downChannel.CloseAsync();
        await upChannel.CloseAsync();
    }