if (socket.Connected) {
    if (socket.Poll(1, SelectMode.SelectRead))
    {
        socket.Close();
        break;
    }

    try
    {
        int length = socket.Receive(data);
        string mes = Encoding.UTF8.GetString(data, 0, length);
        ClientManager.GetInstance().BroadcastMessage(mes);
        Console.WriteLine(mes);
    }
    catch (Exception e) {
        Console.WriteLine("断开链接");
    }
                    
}

socket.Connected 表示获取上次连接的状态