C#写的一段与HTTP响应的接收和发送消息的代码没法跑通求教原因

[yxlovemoney]

首先是这个在线HTTP接口测试工具 https://getman.cn/AJzpc

然后是我下面写的WINFORM代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using System.Net;
using System.Threading;
using System.Net.Sockets;
using System.Diagnostics;

namespace myInitialProject
{
    public partial class Form2 : Form
    {
        Thread serverThread;
        Thread clientThread;
        Socket serverSocket;


        private byte[] result = new byte[1024];
        //Socket clientSocket;
        public Form2()
        {
            InitializeComponent();
        }


        public void ServerStart()
        {
            listBoxInfo.Items.Add("Server Start...");
            string host = "127.0.0.1"; // Form1就通过IPAddress.Any去定义
            int nPort = 10000;
            serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            serverSocket.Bind(new IPEndPoint(IPAddress.Parse(host), nPort));
            serverSocket.Listen(10);
            serverThread = new Thread(ListenClientConnect); // 监听客户端
            serverThread.Start();
        }

        /// <summary>
        /// 监听客户端连接
        /// </summary>
        public void ListenClientConnect()
        {
            while (true)
            {
                Socket clientSocket = serverSocket.Accept();
                //clientSocket.Send(Encoding.UTF8.GetBytes("已连接服务器"));
                Thread receiveThread = new Thread(ReceiveMessage);
                //设置为后台线程，随着主线程退出而退出 
                receiveThread.IsBackground = true;
                receiveThread.Start(clientSocket);
            }
        }

        /// <summary>
        /// 接收信息
        /// </summary>
        /// <param name="clientSocket"></param>
        public void ReceiveMessage(object clientSocket)
        {
            Socket myClientSocket = (Socket)clientSocket;
            byte[] data = new byte[1024];
            int nReceiveNumber;



            byte[] tempData = new byte[1024 * 2]; // 浏览器发来的数据
            int reciverNumber = myClientSocket.Receive(tempData);
            string tempStr = Encoding.UTF8.GetString(tempData, 0, reciverNumber);

            string resdata = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff") + "  server request time:" + 0;
            byte[] body = Encoding.UTF8.GetBytes(resdata);
            byte[] head = Encoding.UTF8.GetBytes(@"HTTP/1.1 200 OK
                                Content-Length: " + body.Length + @"
                                Content-Type: text/plain
                                Date: " + string.Format("{0:R}", DateTime.Now) + @"
                                Server: Cftea Web Server" + resdata);
            StringBuilder sb = new StringBuilder();
            sb.Append("HTTP/1.1 200 OK\r\n");
            sb.Append("Content-Type: text/plain\r\n");
            sb.Append("\r\n");
            sb.Append("测试返回的数据\r\n");
            byte[] responseData = Encoding.UTF8.GetBytes(sb.ToString());
            myClientSocket.Send(responseData);
            myClientSocket.Close();
            /*while (true)
            {
                try
                {
                    
                    // 接收数据
                    nReceiveNumber = myClientSocket.Receive(result);
                    if (nReceiveNumber == 0)
                    {
                        return;
                    }

                   

                    string strMessage = Encoding.UTF8.GetString(result, 0, nReceiveNumber);
                    // 这里打印出客户端发送回来的消息
                    Trace.WriteLine("接收到的返回信息:" + myClientSocket.RemoteEndPoint.ToString() + "  " + strMessage);
                    // 发送回客户端
                    //string strWelcome = "已连接上服务器";
                    
                    // 取得字符串的字节序列
                    //data = Encoding.UTF8.GetBytes(strWelcome);
                    //myClientSocket.Send(data, data.Length, SocketFlags.None);
                    // 短连接 发送完关闭SOCKET
                    //myClientSocket.Close();
                    if (myClientSocket.Connected)
                    {
                        // 判断客户端是否已关闭
                        // 此方法不能检测某些类型的连接问题，
                        // 例如，网络电缆中断或远程主机意外关闭。您必须尝试发送或接收数据以检测这些类型的错误。
                        if (myClientSocket.Poll(0, SelectMode.SelectRead))
                        {
                            
                            {
                                
                                //if (nRead == 0)
                                {
                                    myClientSocket.Close();
                                    MessageBox.Show("客户端已关闭");
                                    break;
                                }
                            }
                        }
                        else
                        {
                            MessageBox.Show("客户端未关闭");
                        }
                    }

                }
                catch (System.Exception ex)
                {
                    MessageBox.Show("server listening Error: " + ex.Message);
                    // 禁止发送和上传
                    //myClientSocket.Shutdown(SocketShutdown.Both);
//                     if(myClientSocket.Poll(-1, SelectMode.SelectRead))
//                     {
//                         byte[] judgeData = new byte[1];
//                         int nRead = myClientSocket.Receive(judgeData, SocketFlags.Peek);
//                         if(nRead  != 0)
//                             myClientSocket.Close();
//                     }
                    
                   break;
                }
            }*/
        }

        /// <summary>
        /// 监听按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnListen_Click(object sender, EventArgs e)
        {
            ServerStart();
        }

        private void Form2_FormClosed(object sender, FormClosedEventArgs e)
        {
            try
            {
                if (serverSocket != null)
                {
                    serverSocket.Close();
                }
                if (serverThread != null)
                {
                    // Thread对象有个IsBackground属性，设置为true即可，在主线程关闭时，子线程随之关闭
                    serverThread.IsBackground = true;
                }
            }
            catch (System.Exception ex)
            {
                MessageBox.Show(ex.Message);

            }
        }
    }
}

这段代码用这个在线测试工具是没通过，总是这样的结果


但我用POSTMAN做本地测试是可以通过的啊



也试过放到别人服务器上去测试，也是不行，


按道理来说不是本地测试通过，就行了吗？ 为什么真正放服务器上跑就不行呢？
这到底是什么原因？ 请各位赐教！