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using System;
using System.Net;
using System.Net.Sockets;
const char DELIM = ' ';
const int DELAY_DURATION_S = 990;
short ReadPort() => args.Length != 0 && short.TryParse(args[0], out var port) ? port : (short)22;
IList<string> ReadBanner() => Console.In.ReadToEnd().Split(DELIM, StringSplitOptions.RemoveEmptyEntries);
async Task SshClientHandler(TcpClient client, IEnumerable<string> banner)
{
var remote = client.Client.RemoteEndPoint;
Console.WriteLine($"{remote}: Client connected.");
try
{
using (client)
{
var stream = client.GetStream();
var writer = new StreamWriter(stream) { AutoFlush = true };
while (true)
{
foreach (var word in banner)
{
await writer.WriteAsync($"{word}{DELIM}");
await Task.Delay(DELAY_DURATION_S);
}
Console.WriteLine($"{remote}: Client read it all!");
}
}
}
catch (Exception ex)
{
Console.WriteLine($"{remote}: Client handler error: {ex.Message}");
}
finally
{
Console.WriteLine($"{remote}: Client hung up");
}
}
// main
var banner = ReadBanner();
var port = ReadPort();
var listener = new TcpListener(IPAddress.Any, port);
using (listener)
{
listener.Start();
Console.WriteLine($"Listening on port {port}...");
while (true)
{
try
{
var client = await listener.AcceptTcpClientAsync();
_ = Task.Run(() => SshClientHandler(client, banner));
}
catch (Exception ex)
{
Console.WriteLine($"Accept error: {ex.Message}");
}
}
}
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