Java实现UDP单播

对于最近所做的Android手机端遥控器APP，用到了UDP组播和广播方面的知识，虽然网络传输方面并不是由我负责，但是由于期间遇到一些问题，所以我的求知欲有蠢蠢欲动，自己就去了解了一下这方面的知识，首先从UDP单播开始给大家分享一下我在学习过程中的感悟。对于UDP的概念在这里就不多做介绍了。

参考链接

http://blog.csdn.net/ljheee/article/details/51722792 

查阅了一些前人的博客，对于我而言感觉这位大神写的特别的好，分析很到位，代码也很简洁，直接从用Java来演绎了UDP的使用。 
http://blog.csdn.net/a10615/article/details/52395592 

然后结合了这位前辈对UDP连接客户端和服务端的API的介绍结合起来理解运用起来就更加理解了。



UDP单播客户端代码



/**
 * UDP单播的例子
 * @author WangHang
 *
 */
public class UdpClient {
    public static void main(String[] args) {
        BufferedReader reader =  new BufferedReader(new InputStreamReader(System.in));
        DatagramSocket clientSocket = null;
        byte[] receiveData = new byte[1024];
        try {
            clientSocket = new DatagramSocket();
            InetAddress inetAddress = InetAddress.getByName("localhost");
//          其实此处的connect方法并不是太符合UDP的设计理念
//          因为UDP是面向非连接的，说的简单点，瞎发就行了至于有没有人收到，关我神马事,所以还是采用数据包指定IP和端口的方法吧
            clientSocket.connect(inetAddress, 8899);
            String data = reader.readLine();
            byte[] sendData = data.getBytes("utf-8");
            DatagramPacket datagramPacket = new DatagramPacket(sendData, sendData.length);
//          当Client没有事先连接到目标IP的端口时（没有调用上面的connect方法），可以在发送的数据包中加上对应的IP和端口
//          DatagramPacket datagramPacket = new DatagramPacket(sendData, sendData.length,inetAddress,8899);
            clientSocket.send(datagramPacket);
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            clientSocket.receive(receivePacket);
            InetAddress address = receivePacket.getAddress();
            System.out.println(address);
            if (address != null) {
                String receive = new String(receivePacket.getData());
                System.out.println(receive);
            }

        } catch (SocketException e) {
            e.printStackTrace();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (clientSocket != null) {
                clientSocket.close();
            }
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}


UDP单播服务端代码



/**
 * UDP单播服务端测试代码
 * @author WangHang
 *
 */
public class UdpServer {

    public static void main(String[] args) {
        DatagramSocket serverSocket = null;
        try {
            serverSocket = new DatagramSocket(8899);
            byte [] receiveData = new byte[1024];
            while (true) {
                DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
                serverSocket.receive(receivePacket);
                System.out.println(new String(receiveData));
                InetAddress address = receivePacket.getAddress();
                System.out.println(address);
                int port = receivePacket.getPort();
//              接收到消息之后回发一个消息给Client
                byte[] sendData = "wanghang".getBytes("utf-8"); 
                DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, address,port);
                serverSocket.send(sendPacket);
            }
        } catch (SocketException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            serverSocket.close();
        }
    }
}



注意事项

这里一定要注意这两段代码只是为了更好理解UDP单播的使用，在实际使用当中一定要将他们都写在单独的线程当中，因为网络连接和发送数据是很耗时的。为了便于测试该测试代码直接使用的localhost，如果要通过真实的网络传输，要自己设置目标的IP，测试起来很简单，先运行server端代码，再运行Client端代码，然后就在控制台上输入你要发送的字符串，回车键之后，就会打印出server端接收到的结果。

1. Linux 服务端



#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#define BUF_SIZE 88
#define PORT     55555

int main(int argc, char *argv[])
{
    //建立套接字
    int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);           //IPV4,数据报套接字类型,不指定协议

    //说明本服务器地址
    const struct sockaddr_in srvaddr = {
        .sin_family = AF_INET,                              //协议类型IPV4
        .sin_port = htons(PORT),                            //端口号-网络字节序
        .sin_addr.s_addr = htonl(INADDR_ANY)                //IP地址-任意地址
    };

    //绑定地址
    bind(sock_fd, (const struct sockaddr *)&srvaddr, sizeof(srvaddr));

    //接收数据
    char buf[BUF_SIZE] = { 0 };
    struct sockaddr_in cliaddr;
    socklen_t cliaddrlen = sizeof(cliaddr);
    while (1)
    {
        bzero(buf, BUF_SIZE);
        bzero(&cliaddr, cliaddrlen);

        recvfrom(sock_fd, buf, BUF_SIZE, 0, (struct sockaddr *)&cliaddr, &cliaddrlen);

        fprintf(stdout, "Recv from [%s - %hu]:%s",
            inet_ntoa(cliaddr.sin_addr),
            ntohs(cliaddr.sin_port),
            buf);
    }

    //关闭套接字
    close(sock_fd);

    return 0;
}

2. Linux 客户端

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#define BUF_SIZE 88
#define PROT     55555
#define ADDR     "192.168.4.194"

int main(int argc, char *argv[])
{
    //建立套接字
    int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);           //IPV4,数据报套接字类型,不指定协议

    //声明将连接地址
    const struct sockaddr_in  srvaddr = {
        .sin_family = AF_INET,                              //协议类型IPV4
        .sin_port = htons(PROT),                            //端口号-网络字节序
        .sin_addr.s_addr = inet_addr(ADDR)                  //IP地址-字符串转IP
    };

    //发送数据
    char buf[BUF_SIZE] = { 0 };
    while (1)
    {
        bzero(buf, BUF_SIZE);

        fprintf(stdout, "Say something: ");
        if (fgets(buf, BUF_SIZE, stdin) == NULL)
            break;

        sendto(sock_fd, buf, strlen(buf), 0, (const struct sockaddr*)&srvaddr, sizeof(srvaddr));
    }

    //关闭套接字
    close(sock_fd);

    return 0;
}

3. Windows 客户端



#include <stdio.h>
#include <WinSock2.h>
#pragma comment( lib, "ws2_32.lib")

#define BUF_SIZE 88
#define PROT     55555
#define ADDR     "192.168.4.194"

int main(int argc, char *argv[])
{
    //初始化SOCKET
    WSADATA wsaData;
    int err = WSAStartup(MAKEWORD(1, 1), &wsaData);
    if (err != 0)
    {
        return -1;
    }

    if (LOBYTE(wsaData.wVersion) != 1 || HIBYTE(wsaData.wVersion) != 1)
    {
        WSACleanup();
        return -1;
    }

    //建立套接字
    SOCKET sock_fd = socket(AF_INET, SOCK_DGRAM, 0);        //IPV4,数据报套接字类型,不指定协议

    //声明将连接地址
    SOCKADDR_IN srvaddr = {
        .sin_family = AF_INET,                              //协议类型IPV4
        .sin_port = htons(PROT),                            //端口号-网络字节序
        .sin_addr.s_addr = inet_addr(ADDR)                  //IP地址-字符串转IP
    };

    //发送数据
    char buf[BUF_SIZE] = { 0 };
    while (1)
    {
        memset(buf, 0, BUF_SIZE);

        fprintf(stdout, "Say something: ");
        if (fgets(buf, BUF_SIZE, stdin) == NULL)
            break;

        sendto(sock_fd, buf, strlen(buf), 0, (const struct sockaddr*)&srvaddr, sizeof(srvaddr));
    }

    //关闭套接字
    closesocket(sock_fd);

    return 0;
}

4. 测试效果

客户端 



服务端 

无论是tcp还是udp 服务器都必须绑定prot、Ip，客户端可以有选择性。

udp单播： 单播只能是发送方往接收方指定的IP 端口发送数据

组播需具备的条件  1、接收方设置组播属性及组播号  2、发送方往接收方定义的组播地址发送  3、服务器客户端端口号需要一致

广播需具备的条件 1、接收方设置广播属性  2、发送方往接收方定义的组播地址发送  3、服务器客户端端口号需要一致


组播和单播的区别：组播可以多设置一个IP（这里称为为组播地址224打头的），发送方除了可以往接收方绑定的IP发送，也可以                                                                                                                                                             往接收方设置的组播ip发送数据。

组播和广播的区别：广播需要设置启动接收广播属性，发送方除了可以往接收方绑定的IP发送，也可以往255同网段IP发送。

这三种udp模型  客户端的实现没有区别，区别仅仅在于发送的网络IP不一样

 

广播是不会被路由器转发的，特点局域网通信，局域网游戏，客户端的统计 局域网群发等。

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp unicast server code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

/*udp和tcp客户端其实都可以绑定自身的IP端口也可以不绑定，

不绑定的话系统会为你默认分配，而服务器则必须绑定端口 IP*/

#include <Winsock2.h>

#include <iostream>

#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }

    // Step 1. Ask system for a socket.this socket is waiter

    SOCKET sockServer = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sockServer == INVALID_SOCKET)

    {

        return 1;

    }

    //Step 2. bind the socket to a local address and port.接待套接字

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    addrServer.sin_port = 30001;

    if (::bind(sockServer, reinterpret_cast<const sockaddr*>(&addrServer),

        sizeof addrServer) == SOCKET_ERROR)

    {

        return 1;

    }

    char buf[100] = { 0 };

    sockaddr_in addrClient;

    int iSize = sizeof(addrClient);

   //recvfrom是阻塞的

    int iResult = recvfrom(sockServer, buf, 100, 0, reinterpret_cast<sockaddr*>(&addrClient), &iSize);

    closesocket(sockServer);

    WSACleanup();

    return 0;

}

 

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp unicast Client code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#include <Winsock2.h>

#include <iostream>

#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }

    // Step 1. Ask system for a socket.this socket is waiter

    SOCKET sock2Server = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sock2Server == INVALID_SOCKET)

    {

        return 1;

    }

    //绑定自己的port  客户端也可以绑定自己的port ip 指定数据从什么端口出去

    //sockaddr_in addrBind = { 0 };

    //addrBind.sin_family = AF_INET;

    //addrBind.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    //addrBind.sin_port = 30002;

    //if (::bind(sock2Server, reinterpret_cast<const sockaddr*>(&addrBind),

    //    sizeof addrBind) == SOCKET_ERROR)

    //{

    //    return 1;

    //}

    //设置接收方的port ip 下面的端口 ip需要和服务器一致

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    addrServer.sin_port = 30001;

    sendto(sock2Server, "hello", 6, 0, reinterpret_cast<sockaddr*>(&addrServer), sizeof(addrServer));

    closesocket(sock2Server);

    WSACleanup();

    return 0;

}

 

 

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp muticast server code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#include <Winsock2.h>

#include <iostream>

#include <thread>

#include<Ws2tcpip.h>   //需要加上此头文件

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }

    // Step 1. Ask system for a socket.this socket is waiter

    SOCKET sockServer = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sockServer == INVALID_SOCKET)

    {

        return 1;

    }

    //Step 2. bind the socket to a local address and port.接待套接字

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    addrServer.sin_port = 30001;

    if (::bind(sockServer, reinterpret_cast<const sockaddr*>(&addrServer),

        sizeof addrServer) == SOCKET_ERROR)

    {

        return 1;

    }

    //设置接收组播属性 

    ip_mreq mrq;

    mrq.imr_multiaddr.S_un.S_addr = inet_addr("224.0.0.11");//设置组播地址 满足前面是224即可224.0.0.1不能用

    mrq.imr_interface.S_un.S_addr = 0;   //设置自动选择网卡上面接收组播

    if (setsockopt(sockServer, IPPROTO_IP, IP_ADD_MEMBERSHIP, reinterpret_cast<const char*>(&mrq), sizeof(mrq))                 ==    SOCKET_ERROR)

    {

        return 1;

    }



    char buf[100] = { 0 };

    sockaddr_in addrClient;

    int iSize = sizeof(addrClient);

    int iResult = recvfrom(sockServer, buf, 100, 0, reinterpret_cast<sockaddr*>(&addrClient), &iSize);

    closesocket(sockServer);

    WSACleanup();

    return 0;

}

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp muticast client code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#include <Winsock2.h>

#include <iostream>

#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }



    SOCKET sock2Server = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sock2Server == INVALID_SOCKET)

    {

        return 1;

    }

 

    //设置接收方的port ip 下面的端口

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    //点对点的也可以

    //addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    //往服务器组播地址发也可以，相比单播多一个选择性 

    addrServer.sin_addr.S_un.S_addr = inet_addr("224.0.0.11");

    addrServer.sin_port = 30001;

    sendto(sock2Server, "hello", 6, 0, reinterpret_cast<sockaddr*>(&addrServer), sizeof(addrServer));

    closesocket(sock2Server);

    WSACleanup();

    return 0;

}

 

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp broadcast server code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------


//具备广播的条件  1、接收方设置广播属性 2、发送方往同网段的255IP地址发送 3、服务器客户端端口号需要一致

#include <Winsock2.h>

#include <iostream>

#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }

    // Step 1. Ask system for a socket.this socket is waiter

    SOCKET sockServer = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sockServer == INVALID_SOCKET)

    {

        return 1;

    }

    //Step 2. bind the socket to a local address and port.接待套接字

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    addrServer.sin_port = 30001;

    if (::bind(sockServer, reinterpret_cast<const sockaddr*>(&addrServer),

        sizeof addrServer) == SOCKET_ERROR)

    {

        return 1;

    }

    //设置接收广播属性 要设置了广播属性才可以接收广播消息   
    bool bEnableBroadcast = true;

    if (setsockopt(sockServer, SOL_SOCKET, SO_BROADCAST, reinterpret_cast<const char*>(&bEnableBroadcast),                                               sizeof(bEnableBroadcast)) == SOCKET_ERROR)

    {

        return 1;

    }

    

    char buf[100] = { 0 };

    sockaddr_in addrClient;

    int iSize = sizeof(addrClient);

    int iResult = recvfrom(sockServer, buf, 100, 0, reinterpret_cast<sockaddr*>(&addrClient), &iSize);

    closesocket(sockServer);

    WSACleanup();

    return 0;

}

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  udp broadcast client code

/------------------------------------------------------------------------------------------------------------------------------------------------------------------------

#include <Winsock2.h>

#include <iostream>

#include <thread>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

int main(void)

{

    /* 初始化winsock2库 */

    //Step 0. Initialize winsock2 library...

    WSADATA wsaData;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)

    {

        return 1;

    }

    // Step 1. Ask system for a socket.this socket is waiter

    SOCKET sock2Server = ::socket(PF_INET, SOCK_DGRAM, 0);

    if (sock2Server == INVALID_SOCKET)

    {

        return 1;

    }

    //广播中服务器设置了广播属性的话 下

    //设置接收方的port ip 下面的端口

    sockaddr_in addrServer = { 0 };

    addrServer.sin_family = AF_INET;

    //点对点的也可以

    //addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.134");

    //往255这个网段发的话 只要是设置了广播属性的服务器都可以接收到数据 
    addrServer.sin_addr.S_un.S_addr = inet_addr("88.88.106.255");

    addrServer.sin_port = 30001;

    sendto(sock2Server, "hello", 6, 0, reinterpret_cast<sockaddr*>(&addrServer), sizeof(addrServer));

    closesocket(sock2Server);

    WSACleanup();

    return 0;

}

 

UDP单播通信测试案例C#
UDP单播
一段代码做纪念
Client
// An highlighted block
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Threading;
using System.Net.Sockets;
using CRC;

namespace CRC
{
    public partial class MainForm : Form
    {
        private IPEndPoint ServerInfo;
        private Socket ClientSocket;
        private EndPoint Remote;
        //信息接收缓存
        private Byte[] MsgBuffer;
        //信息发送存储
        private Byte[] MsgSend;
        byte[] data = new byte[1024];
        string input, stringData;
        private Thread CThread;//服务端运行的线程

        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            //this.CmdSend.Enabled = false;
            //this.CmdExit.Enabled = false;
            MsgBuffer = new Byte[65535];
            MsgSend = new Byte[65535];
            //允许子线程刷新数据
            CheckForIllegalCrossThreadCalls = false;
            Userport.Text = "6888";
            UserIP.Text = "192.168.10.4";
            //127.0.0.1是回环地址，用于测试本机内连接
            //192.168.10.4用来发到其他的主机上
        }
        bool flag = true;//定义一个bool变量，标识是否接收数据
        Thread thread;//创建线程对象
        UdpClient udp;
        private void CmdEnter_Click(object sender, EventArgs e)
        {
            this.CmdEnter.Enabled = false;
            this.CmdExit.Enabled = true;

            //设置服务IP，设置TCP端口号  
            IPEndPoint ipep = new IPEndPoint(IPAddress.Parse(this.UserIP.Text), 6888);

            //定义网络类型，数据连接类型和网络协议UDP  
            Socket ClientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

            string welcome = "Hello! ";
            data = Encoding.Unicode.GetBytes(welcome);
            ClientSocket.SendTo(data, data.Length, SocketFlags.None, ipep);
            IPEndPoint sder = new IPEndPoint(IPAddress.Any, 0);
            EndPoint Remote = (EndPoint)sder;

            data = new byte[1024];
            //对于不存在的IP地址，加入此行代码后，可以在指定时间内解除阻塞模式限制  
            //server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 100);  
            int recv = ClientSocket.ReceiveFrom(data, ref Remote);
            this.ReceiveMsg.AppendText("Message received from "+Remote.ToString());
            this.ReceiveMsg.AppendText(Encoding.Unicode.GetString(data, 0, recv));

            flag = true;//标识接收数据
            thread = new Thread(() =>//新开线程，执行接收数据操作
            {
                while (flag)//如果标识为true
                {
                    try
                    {
                        input = "123456789";
                        ClientSocket.SendTo(Encoding.Unicode.GetBytes(input), Remote);

                        data = new byte[1024];
                        recv = ClientSocket.ReceiveFrom(data, ref Remote);
                        stringData = Encoding.Unicode.GetString(data, 0, recv);
                        this.ReceiveMsg.AppendText(stringData+"\n");
                        string OnePareStr = stringData.Substring(0,4);
                        string TwoPareStr = stringData.Substring(4,4);
                        string ThreePareStr = stringData.Substring(8, 4);
                        string FourPareStr = stringData.Substring(12, 4);
                        string FivePareStr = stringData.Substring(16, 4);
                        string deData = Decode(OnePareStr, TwoPareStr, ThreePareStr, FourPareStr, FivePareStr);
                        this.ReceiveMsg.AppendText(deData + "\n");
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show(ex.Message);//错误提示
                    }
                    //Thread.Sleep(2000);//线程休眠2秒
                }
            });
            thread.Start();//启动线程
             
        }

        private string Decode(string onePareStr, string twoPareStr, string threePareStr, string fourPareStr, string fivePareStr)
        {
            string mycode, myc0, myc1, myc2, myc3, myc4;
            Int16 id0, id1, id2, id3, id4;
            id0=System.Convert.ToInt16(onePareStr, 16);
            id1=System.Convert.ToInt16(twoPareStr, 16);
            id2=System.Convert.ToInt16(threePareStr, 16);
            id3=System.Convert.ToInt16(fourPareStr, 16);
            id4=System.Convert.ToInt16(fivePareStr, 16);
            switch (id0){
                case 2:
                    myc0 = "进站触发";
                    break;
                default:
                    myc0 = "";
                    break;
            }
            switch (id1)
            {
                case 1:
                    myc1 = "阎村东";
                    break;
                default:
                    myc1 = "阎村东";
                    break;
            }
            switch (id2)
            {
                case 1:
                    myc2 = "阎村东";
                    break;
                default:
                    myc2 = "阎村东";
                    break;
            }
            switch (id3)
            {
                case 2:
                    myc3 = "紫草坞";
                    break;
                default:
                    myc3 = "紫草坞";
                    break;
            }
            switch (id4)
            {
                case 20:
                    myc4 = "燕山";
                    break;
                default:
                    myc4 = "燕山";
                    break;
            }
            mycode = myc0+ ",起始站" + myc1 + ",当前站" + myc2 + ",下一站" + myc3 + ",终点站" + myc4;
            return mycode;
        }

        private void CmdExit_Click(object sender, EventArgs e)
        {
            ClientSocket.Close();
            
            this.CmdEnter.Enabled = true;
            this.CmdExit.Enabled = false;


        }
        
    }
}

Server
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Threading;
using System.Net;

namespace Server
{
    public partial class MainForm : Form
    {
        //声明将要用到的类
        private IPEndPoint ServerInfo;//存放服务器的IP和端口信息
        private EndPoint Remote;
        private Socket ServerSocket;//服务端运行的SOCKET
        private Thread ServerThread;//服务端运行的线程
        

        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            this.CmdStar.Enabled = true;
            this.CmdStop.Enabled = false;
            ServerIP.Text= "192.168.10.4";
            RemoteIp.Text= "192.168.10.5";
        }
        // udp.Connect("127.0.0.1", 6888);//127.0.0.1是回环地址，用于测试本机内连接
        //udp.Connect("192.168.1.255", 6888);//192.168.10.5用来发到其他的主机上
        private void CmdStar_Click(object sender, EventArgs e)
        {
            ServerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            //提供一个 IP 地址，指示服务器应侦听所有网络接口上的客户端活动
            ServerInfo = new IPEndPoint(IPAddress.Parse(this.ServerIP.Text), Convert.ToInt32(ServerPort.Text));
            ServerSocket.Bind(ServerInfo);//将SOCKET接口和IP端口绑定

            ServerThread = new Thread(new ThreadStart(RecieveAccept));//将接受客户端连接的方法委托给线程
            ServerThread.Start();//线程开始运行

            CheckForIllegalCrossThreadCalls = false;//不捕获对错误线程的调用

            this.CmdStar.Enabled = false;
            this.CmdStop.Enabled = true;
            this.StateMsg.Text = "服务正在运行..." + " 运行端口：6888";
            this.ClientList.Items.Add("服务于 " + DateTime.Now.ToString() + " 开始运行.");
        }
        
        //接受客户端连接的方法
        private void RecieveAccept()
        {
            int recv;
            byte[] revData = new byte[1024];
            byte[] sendData = new byte[1024];
            //得到客户机IP 
            IPEndPoint ipep = new IPEndPoint(IPAddress.Parse(this.RemoteIp.Text), Convert.ToInt32(RemotePort.Text));
            EndPoint Remote = ipep;
            recv = ServerSocket.ReceiveFrom(revData, ref Remote);
            receiveMsg.Items.Add("我是服务端，客户端连接成功");
            receiveMsg.Items.Add(Encoding.Unicode.GetString(revData, 0, recv));

            //客户机连接成功后，发送欢迎信息
            string welcome = "Welcome !";
            sendData = Encoding.Unicode.GetBytes(welcome);
            ServerSocket.SendTo(sendData, sendData.Length, SocketFlags.None, Remote);

            while (true)
            {
                //接受信息
                recv = ServerSocket.ReceiveFrom(revData, ref Remote);
                receiveMsg.Items.Add(Encoding.Unicode.GetString(revData, 0, recv));
                //发送信息
                string recvDateSucceed = string.Format("服务器已收到.");
                sendData = Encoding.Unicode.GetBytes(Station_Reporting());
                ServerSocket.SendTo(sendData, sendData.Length, SocketFlags.None, Remote);
                //设定周期
                Thread.Sleep(3000);//阻止设定时间 
            }
        }

        private string Station_Reporting()
        {
            //0002 0001 0001 0002 0014  
            //进站触发（0x0002），起始站阎村东（0x0001），当前站阎村东（0x0002），下一站紫草坞（0x0014），终点站燕山（0x0014）
            string baowen = "00020001000100020014";

            return baowen;
        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            string msg = sendMsg.Text;
            //发送UDP数据包 
            Byte[] data = Encoding.Unicode.GetBytes(msg);
            ServerSocket.SendTo(data, Remote); ;
            receiveMsg.Items.Add("来自服务器的消息：" + sendMsg.Text);
         

        }

        private void CmdStop_Click(object sender, EventArgs e)
        {
            ServerThread.Abort();//线程终止
            ServerSocket.Close();//关闭socket

            this.CmdStar.Enabled = true;
            this.CmdStop.Enabled = false;
            this.StateMsg.Text = "等待运行...";
            this.ClientList.Items.Add("服务于 " + DateTime.Now.ToString() + " 停止运行.");
        }
         
        private void MainForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            ServerThread.Abort();//线程终止
            ServerSocket.Close();//关闭SOCKET
            Application.Exit();
        }

        private void label5_Click(object sender, EventArgs e)
        {

        }
    }
}