아래 소스인데요… 유튜브에선 이 소스가 잘돌아 갑니다.
확인해본 결과 아무 문제 없는데요 이부분을 빼면
BeginReceive(…, ReceiveCallback, ,… , _cli_socket);
부분으로 해서 ReceiveCallabck 부분 처리하는 데에
Socket current = (Socket)AR.AsyncState; 이부분이 밑줄이 계속 가더라고요
오류 :
null 리터럴 또는 가능한 null 값을 null을 허용하지 않는 형식으로 변환하는 중입니다.
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Sockets;
using System.Text;
namespace MultiServer
{
class Program
{
private static readonly Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
private static readonly List<Socket> clientSockets = new List<Socket>();
private const int BUFFER_SIZE = 2048;
private const int PORT = 100;
private static readonly byte[] buffer = new byte[BUFFER_SIZE];
static void Main()
{
Console.Title = "Server";
SetupServer();
Console.ReadLine(); // When we press enter close everything
CloseAllSockets();
}
private static void SetupServer()
{
Console.WriteLine("Setting up server...");
serverSocket.Bind(new IPEndPoint(IPAddress.Any, PORT));
serverSocket.Listen(0);
serverSocket.BeginAccept(AcceptCallback, null);
Console.WriteLine("Server setup complete");
}
/// <summary>
/// Close all connected client (we do not need to shutdown the server socket as its connections
/// are already closed with the clients).
/// </summary>
private static void CloseAllSockets()
{
foreach (Socket socket in clientSockets)
{
socket.Shutdown(SocketShutdown.Both);
socket.Close();
}
serverSocket.Close();
}
private static void AcceptCallback(IAsyncResult AR)
{
Socket socket;
try
{
socket = serverSocket.EndAccept(AR);
}
catch (ObjectDisposedException) // I cannot seem to avoid this (on exit when properly closing sockets)
{
return;
}
clientSockets.Add(socket);
socket.BeginReceive(buffer, 0, BUFFER_SIZE, SocketFlags.None, ReceiveCallback, socket);
Console.WriteLine("Client connected, waiting for request...");
serverSocket.BeginAccept(AcceptCallback, null);
}
private static void ReceiveCallback(IAsyncResult AR)
{
Socket current = (Socket)AR.AsyncState;
int received;
try
{
received = current.EndReceive(AR);
}
catch (SocketException)
{
Console.WriteLine("Client forcefully disconnected");
// Don't shutdown because the socket may be disposed and its disconnected anyway.
current.Close();
clientSockets.Remove(current);
return;
}
byte[] recBuf = new byte[received];
Array.Copy(buffer, recBuf, received);
string text = Encoding.ASCII.GetString(recBuf);
Console.WriteLine("Received Text: " + text);
if (text.ToLower() == "get time") // Client requested time
{
Console.WriteLine("Text is a get time request");
byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());
current.Send(data);
Console.WriteLine("Time sent to client");
}
else if (text.ToLower() == "exit") // Client wants to exit gracefully
{
// Always Shutdown before closing
current.Shutdown(SocketShutdown.Both);
current.Close();
clientSockets.Remove(current);
Console.WriteLine("Client disconnected");
return;
}
else
{
Console.WriteLine("Text is an invalid request");
byte[] data = Encoding.ASCII.GetBytes("Invalid request");
current.Send(data);
Console.WriteLine("Warning Sent");
}
current.BeginReceive(buffer, 0, BUFFER_SIZE, SocketFlags.None, ReceiveCallback, current);
}
}
}