socket网络编程问题

Question

服务端：

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using System.Configuration;
using System.Data.SqlClient;
using System.Text.RegularExpressions;
using MyLibrary;
using System.ComponentModel;
using System.Text;
using System.Security.Cryptography;
using Microsoft.International.Converters.PinYinConverter;
using System.Reflection;
using System.Net;
using System.Net.Sockets;
using System.Threading;

namespace first_project
{
   
    
    static class Program
    {

        
        static Dictionary<string, Socket> clientList = new Dictionary<string, Socket>();
        static void Main(string[] args)
        {


            
            Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            serverSocket.Bind(new IPEndPoint(IPAddress.Parse("127.0.0.1"), 99));
            Console.WriteLine("listening...");
            serverSocket.Listen(10);




            while (true)
            {
                Socket socketCommu = serverSocket.Accept();
                clientList.Add(socketCommu.RemoteEndPoint.ToString().Split(':')[1], socketCommu);
                Console.WriteLine(socketCommu.RemoteEndPoint + ": connected");

                Thread threadReceive = new Thread(Receive);
                threadReceive.IsBackground = true;
                threadReceive.Start(socketCommu);

                Thread threadSend = new Thread(Send);
                threadSend.IsBackground = true;
                threadSend.Start();
            }



        }
		
	static void Receive(object obj)
	{
			
		byte[] buffer;
                Socket socketCommu = obj as Socket;

                        while (true)
			{
				buffer = new byte[3 * 1024 * 1024];
				int r = socketCommu.Receive(buffer);
				if(r == 0) break;
				Console.WriteLine(socketCommu.RemoteEndPoint + ": " + Encoding.UTF8.GetString(buffer, 0, r));
			}
        }

        
		
	static void Send()
        {
            
            Console.WriteLine("input client port:");
            string port = Console.ReadLine();
            Socket socketCommu = clientList[port];
            while (true)
                socketCommu.Send(Encoding.UTF8.GetBytes(Console.ReadLine()));
        }
		
        

        

        
    }
}

客户端:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace client
{
    class Program
    {
        static Socket clientSocket;
       
        static void Main(string[] args)
        {
           
            clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
	    clientSocket.Connect(IPAddress.Parse("127.0.0.1"), 99);
	    Console.WriteLine("server connected");
			
            Thread th = new Thread(Send);
	    th.IsBackground = true;
	    th.Start();
			
	    byte[] buffer;
	    while(true)
	   {
				buffer = new byte[3 * 1024 * 1024];
				int r = clientSocket.Receive(buffer);
				if(r == 0) break;
				Console.WriteLine(clientSocket.RemoteEndPoint +": "+Encoding.UTF8.GetString(buffer, 0, r));
	   }
			
        }

	static void Send()
	{
	    while(true) 
		clientSocket.Send(Encoding.UTF8.GetBytes(Console.ReadLine()));
	}
        

        
    }
}

为什么输入已经连接的客户端端口抛异常提示字典clientList的键不存在？