Does async/await affects tcp server performance?

Question

I am creating a Tcp server in C# 5.0 and I am using the await keyword when calling tcpListener.AcceptTcpClientAsync and networkStream.ReadAsync

Answer 1

I have also issues with an async and these are my findings: https://stackoverflow.com/a/22222578/307976

Also, I have an asynchronous TCP server/client using async example here that scales well.

Answer 2

Try the following implementation of ReceiveInt32Async and ReceiveDataAsync for receiving your length-prefixed messages directly, instead of using tcpClient.GetStream and networkStream.ReadAsync:

public static class SocketsExt
{
    static public async Task<Int32> ReceiveInt32Async(
        this TcpClient tcpClient)
    {
        var data = new byte[sizeof(Int32)];
        await tcpClient.ReceiveDataAsync(data).ConfigureAwait(false);
        return BitConverter.ToInt32(data, 0);
    }

    static public Task ReceiveDataAsync(
        this TcpClient tcpClient,
        byte[] buffer)
    {
        return Task.Factory.FromAsync(
            (asyncCallback, state) =>
                tcpClient.Client.BeginReceive(buffer, 0, buffer.Length, 
                    SocketFlags.None, asyncCallback, state),
            (asyncResult) =>
                tcpClient.Client.EndReceive(asyncResult), 
            null);
    }
}

See if this gives any improvements. On a side note, I also suggest making ReceiveDataFromClientAsync an async Task method and storing the Task it returns inside AsyncTcpClientConnection (for status and error tracking).