According to
If async-await doesn't create any additional threads, then how does it make applications responsive?
a C# task, executed by await ... doesn't create a separate thread for the target Task. However, I observed, that such a task is executed not every time from the same thread, but can switch it's thread.
I still do not understand, what's going on.
public class TestProgram
{
private static async Task HandleClient(TcpClient clt)
{
using NetworkStream ns = clt.GetStream();
using StreamReader sr = new StreamReader(ns);
while (true)
{
string msg = await sr.ReadLineAsync();
Console.WriteLine($"Received in {System.Threading.Thread.CurrentThread.ManagedThreadId} :({msg.Length} bytes):\n{msg}");
}
}
private static async Task AcceptConnections(int port)
{
TcpListener listener = new TcpListener(IPAddress.Parse("127.0.0.1"), port);
listener.Start();
while(true)
{
var client = await listener.AcceptTcpClientAsync().ConfigureAwait(false);
Console.WriteLine($"Accepted connection for port {port}");
var task = HandleClient(client);
}
}
public async static Task Main(string[] args)
{
var task1=AcceptConnections(5000);
var task2=AcceptConnections(5001);
await Task.WhenAll(task1, task2).ConfigureAwait(false);
}
}
This example code creates two listeners for ports 5000 and 5001. Each of it can accept multiple connections and read independently from the socket created.
Maybe it is not "nice", but it works and I observed, that messages received from different sockets are sometimes handled in the same thread, and that the used thread for execution even changes.
Accepted connection for port 5000
Accepted connection for port 5000
Accepted connection for port 5001
Received new message in 5 :(17 bytes):
Port-5000 Message from socket-1
Received new message in 7 :(18 bytes):
Port-5000 Message from socket-1
Received new message in 7 :(18 bytes):
Port-5000 Message from socket-1
Received new message in 7 :(20 bytes):
Port-5000 Message from socket-2
Received new message in 7 :(18 bytes):
Port-5000 Message from socket-2
Received new message in 7 :(18 bytes):
Port-5001 Message from socket-3
Received new message in 8 :(17 bytes):
Port-5001 Message from socket-3
(texts manually edit for clarity, byte lengths are not valid)
If there is heavy load (I didn't test it yet), how many threads would be involved in order to execute those parallel tasks? I heard about a thread pool, but do not know, how to have some influence on it.
Or is it totally wrong asking that and I do not at all have to care about what particular thread is used and how many of them are involved?
