组播例子

编译程序用下列命令:
gcc -Wall mcastclient.c -o mcastclient
gcc -Wall mcastserver.c -o mcastserver
运行程序用如下命令:
./mcastserver 230.1.1.1 7838
客户端程序运行命令为:
./mcastclient 230.1.1.1 7838 192.168.100.1 12345
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#define BUFLEN 255
/*********************************************************************
*filename: mcastserver.c
*purpose: 演示组播编程的基本步骤,组播服务器端,关键在于加入组
*tidied by: zhoulifa( zhoulifa@163.com) 周立发( http://zhoulifa.bokee.com)
Linux爱好者 Linux知识传播者 SOHO族 开发者 最擅长C语言
*date time:2007-01-25 13:20:00
*Note: 任何人可以任意复制代码并运用这些文档,当然包括你的商业用途
* 但请遵循GPL
*Thanks to: Google.com
*Hope:希望越来越多的人贡献自己的力量,为科学技术发展出力
* 科技站在巨人的肩膀上进步更快!感谢有开源前辈的贡献!
*********************************************************************/
int main(int argc, char **argv)
{
    struct sockaddr_in peeraddr;
    struct in_addr ia;
    int sockfd;
    char recmsg[BUFLEN + 1];
    unsigned int socklen, n;
    struct hostent *group;
    struct ip_mreq mreq;
   
    /* 创建 socket 用于UDP通讯 */
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
     {
        printf("socket creating err in udptalk\n");
        exit(1);
      }
    /* 设置要加入组播的地址 */
     bzero(&mreq, sizeof(struct ip_mreq));
     if (argv[1])
      {
         if ((group = gethostbyname(argv[1])) == (struct hostent *) 0)
          {
            perror("gethostbyname");
            exit(errno);
          }
      }
     else
      {
         printf("you should give me a group address, 224.0.0.0-239.255.255.255\n");
         exit(errno);
      }
      bcopy((void *) group->h_addr, (void *) &ia, group->h_length);
      /* 设置组地址 */
      bcopy(&ia, &mreq.imr_multiaddr.s_addr, sizeof(struct in_addr));
       /* 设置发送组播消息的源主机的地址信息 */
      mreq.imr_interface.s_addr = htonl(INADDR_ANY);
       /* 把本机加入组播地址,即本机网卡作为组播成员,只有加入组才能收到组播消息 */
     if (setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,sizeof(struct ip_mreq)) == -1)
      {
        perror("setsockopt");
        exit(-1);
       }
     socklen = sizeof(struct sockaddr_in);
     memset(&peeraddr, 0, socklen);
     peeraddr.sin_family = AF_INET;
     if (argv[2])
        peeraddr.sin_port = htons(atoi(argv[2]));
     else
        peeraddr.sin_port = htons(7838);
     if (argv[1])
      {
         if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0)
          {
              printf("Wrong dest IP address!\n");
              exit(0);
          }
       }
      else
       {
          printf("no group address given, 224.0.0.0-239.255.255.255\n");
           exit(errno);
        }
/* 绑定自己的端口和IP信息到socket上 */
    if (bind(sockfd, (struct sockaddr *) &peeraddr,sizeof(struct sockaddr_in)) == -1)
     {
        printf("Bind error\n");
        exit(0);
      }
     
int len = 0;
      len = sizeof(struct sockaddr_in);
      printf("%s\n", inet_ntoa(peeraddr.sin_addr));
     printf("port:%d\n", peeraddr.sin_port); 
    
/* 循环接收网络上来的组播消息 */
for (;;)
{
    bzero(recmsg, BUFLEN + 1);
    n = recvfrom(sockfd, recmsg, BUFLEN, 0,(struct sockaddr *) &peeraddr, &socklen);
    if (n < 0)
    {
      printf("recvfrom err in udptalk!\n");
      exit(4);
    }
    else
    {
      /* 成功接收到数据报 */
      //int len = 0;
      len = sizeof(struct sockaddr_in);
      printf("%s\n", inet_ntoa(peeraddr.sin_addr));
     printf("port:%d\n", peeraddr.sin_port); 
     
      recmsg[n] = 0;
      printf("peer:%s", recmsg);
    }
}
}
 
 
 
 
 
///////////////////////////////client/////////////////////////////////
 
 
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFLEN 255
/*********************************************************************
*filename: mcastclient.c
*purpose: 演示组播编程的基本步骤,其实这就是一个基本的UDP客户端程序
*tidied by: zhoulifa( zhoulifa@163.com) 周立发( http://zhoulifa.bokee.com)
Linux爱好者 Linux知识传播者 SOHO族 开发者 最擅长C语言
*date time:2007-01-25 13:10:00
*Note: 任何人可以任意复制代码并运用这些文档,当然包括你的商业用途
* 但请遵循GPL
*Thanks to: Google.com
*Hope:希望越来越多的人贡献自己的力量,为科学技术发展出力
* 科技站在巨人的肩膀上进步更快!感谢有开源前辈的贡献!
*********************************************************************/
int main(int argc, char **argv)
{
    struct sockaddr_in peeraddr, myaddr;
    int sockfd;
    char recmsg[BUFLEN + 1];
    unsigned int socklen;
   
    /* 创建 socket 用于UDP通讯 */
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
     {
         printf("socket creating error\n");
         exit(1);
      }
    socklen = sizeof(struct sockaddr_in);
   
    /* 设置对方的端口和IP信息 */
    memset(&peeraddr, 0, socklen);
    peeraddr.sin_family = AF_INET;
    if (argv[2])
     {
         peeraddr.sin_port = htons(atoi(argv[2]));
      }
    else
     {
        peeraddr.sin_port = htons(7838);
      }
    if (argv[1])
     {
        /* 注意这里设置的对方地址是指组播地址,而不是对方的实际IP地址 */
        if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0)
         {
            printf("wrong group address!\n");
            exit(0);
          }
      }
    else
     {
         printf("no group address!\n");
         exit(0);
      }
   
    /* 设置自己的端口和IP信息 */
    memset(&myaddr, 0, socklen);
    myaddr.sin_family = AF_INET;
    if (argv[4])
      myaddr.sin_port = htons(atoi(argv[4]));
    else
      myaddr.sin_port = htons(23456);
   
    /*
    if (argv[3])
     {
        if (inet_pton(AF_INET, argv[3], &myaddr.sin_addr) <= 0)
         {
            printf("self ip address error!\n");
            exit(0);
          }
    }
    else
      myaddr.sin_addr.s_addr = INADDR_ANY;
    */
    myaddr.sin_addr.s_addr = INADDR_ANY;
    printf("port:%d\n", myaddr.sin_port);
    /* 绑定自己的端口和IP信息到socket上 */
    if (bind(sockfd, (struct sockaddr *) &myaddr,  sizeof(struct sockaddr_in)) == -1)
     {
        printf("Bind error\n");
        perror("bind");
        exit(0);
      }
     
    int len = 0;
         len = sizeof(struct sockaddr_in);
         getsockname(sockfd, (struct sockaddr *)&myaddr, &len);
         printf("%s\n", inet_ntoa(myaddr.sin_addr));
     printf("port:%d\n", myaddr.sin_port);   
   
    /* 循环接受用户输入的消息发送组播消息 */
    for (;;)
    {
        /* 接受用户输入 */
        bzero(recmsg, BUFLEN + 1);
        if (fgets(recmsg, BUFLEN, stdin) == (char *) EOF)
          exit(0);
        /* 发送消息 */
        if (sendto(sockfd, recmsg, strlen(recmsg), 0,(struct sockaddr *) &peeraddr,sizeof(struct sockaddr_in)) < 0)
         {
            printf("sendto error!\n");
            exit(3);
          }
       
       
         
        printf("'%s' send ok\n", recmsg);
    }

<think>我们将在Qt4.8.6下编写一个UDP例子。由于Qt4.8.6不支持一些Qt5的新特性,我们将使用旧式的信号槽连接,并且注意相关的API在Qt4中的使用方式。主要步骤:1.创建一个QUdpSocket对象。2.绑定到一个端口和地址(注意需要特定的地址)。3.加入。4.接收数据:通过readyRead信号连接到槽函数,读取数据报。5.发送数据:使用writeDatagram发送到地址和端口。注意:地址范围是224.0.0.0到239.255.255.255。我们将编写一个简单的发送和接收程序。程序可以同时发送和接收消息。由于Qt4.8.6不支持lambda表达式,我们将使用传统的信号槽连接方式。代码结构:-创建一个类MulticastUDP,用于封装的发送和接收。 -在main函数中,创建该类的实例,并演示发送和接收。注意:在Qt4中,加入使用QUdpSocket::joinMulticastGroup,但要注意,在绑定之后调用。我们将编写一个简单的示例,每隔一段时间发送一条消息,并接收显示。由于Qt4.8.6没有QTimer::singleShot的lambda支持,我们将使用一个QTimer并连接其timeout信号到一个槽函数来发送消息。以下是代码:</think>### Qt 4.8.6 UDP 示例 (Linux/C++) 以下是一个完整的 UDP 示例,适用于 Linux 平台下的 Qt 4.8.6: #### `multicast.h` 头文件 ```cpp #ifndef MULTICAST_H #define MULTICAST_H #include <QObject> #include <QUdpSocket> #include <QTimer> class Multicast : public QObject { Q_OBJECT public: explicit Multicast(QObject *parent = 0); ~Multicast(); void startReceiver(const QString &multicastGroup, quint16 port); void startSender(const QString &multicastGroup, quint16 port, const QString &message); private slots: void onReadyRead(); void sendMessage(); private: QUdpSocket *m_socket; QTimer *m_timer; QString m_multicastGroup; quint16 m_port; QString m_message; }; #endif // MULTICAST_H ``` #### `multicast.cpp` 实现文件 ```cpp #include "multicast.h" #include <QHostAddress> #include <QNetworkInterface> #include <QDebug> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> Multicast::Multicast(QObject *parent) : QObject(parent), m_socket(0), m_timer(0) { } Multicast::~Multicast() { if (m_socket) { m_socket->close(); delete m_socket; } if (m_timer) { m_timer->stop(); delete m_timer; } } void Multicast::startReceiver(const QString &multicastGroup, quint16 port) { if (m_socket) return; m_socket = new QUdpSocket(this); m_multicastGroup = multicastGroup; m_port = port; // 绑定到端口 if (!m_socket->bind(port, QUdpSocket::ShareAddress)) { qWarning() << "Failed to bind to port" << port; return; } // 加入 QHostAddress groupAddress(multicastGroup); if (!groupAddress.isMulticast()) { qWarning() << multicastGroup << "is not a multicast address"; return; } if (!m_socket->joinMulticastGroup(groupAddress)) { qWarning() << "Failed to join multicast group" << multicastGroup; return; } // 设置TTL(可选) int ttl = 1; // 限制在本地网络 int sockfd = m_socket->socketDescriptor(); if (sockfd != -1) { setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)); } // 连接信号槽 connect(m_socket, SIGNAL(readyRead()), this, SLOT(onReadyRead())); qDebug() << "Listening for multicast on" << multicastGroup << ":" << port; } void Multicast::startSender(const QString &multicastGroup, quint16 port, const QString &message) { if (m_socket) return; m_socket = new QUdpSocket(this); m_multicastGroup = multicastGroup; m_port = port; m_message = message; // 创建定时器用于发送消息 m_timer = new QTimer(this); connect(m_timer, SIGNAL(timeout()), this, SLOT(sendMessage())); m_timer->start(2000); // 每2秒发送一次 qDebug() << "Sending multicast to" << multicastGroup << ":" << port; } void Multicast::onReadyRead() { while (m_socket->hasPendingDatagrams()) { QByteArray datagram; datagram.resize(m_socket->pendingDatagramSize()); QHostAddress sender; quint16 senderPort; m_socket->readDatagram(datagram.data(), datagram.size(), &sender, &senderPort); qDebug() << "Received from" << sender.toString() << ":" << senderPort << "=>" << QString::fromUtf8(datagram); } } void Multicast::sendMessage() { QByteArray datagram = m_message.toUtf8(); QHostAddress groupAddress(m_multicastGroup); // 获取所有网络接口 QList<QNetworkInterface> interfaces = QNetworkInterface::allInterfaces(); foreach (const QNetworkInterface &interface, interfaces) { if (interface.flags() & QNetworkInterface::CanMulticast) { // 设置输出接口 int sockfd = m_socket->socketDescriptor(); if (sockfd != -1) { struct in_addr ifaceAddr; QList<QNetworkAddressEntry> entries = interface.addressEntries(); if (!entries.isEmpty()) { QHostAddress addr = entries.first().ip(); if (addr.protocol() == QAbstractSocket::IPv4Protocol) { ifaceAddr.s_addr = htonl(addr.toIPv4Address()); setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_IF, &ifaceAddr, sizeof(ifaceAddr)); } } } // 发送消息 qint64 sent = m_socket->writeDatagram(datagram, groupAddress, m_port); if (sent == -1) { qWarning() << "Failed to send multicast to" << m_multicastGroup << ":" << m_port; } else { qDebug() << "Sent multicast:" << m_message; } } } } ``` #### `main.cpp` 主程序 ```cpp #include <QCoreApplication> #include <QStringList> #include <QTimer> #include "multicast.h" int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); // 参数处理 QStringList args = QCoreApplication::arguments(); if (args.size() < 4) { qDebug() << "Usage:" << args[0] << "<mode> <multicast_group> <port> [message]"; qDebug() << "Modes: receiver | sender"; qDebug() << "Example:"; qDebug() << " " << args[0] << "receiver 239.255.43.21 45454"; qDebug() << " " << args[0] << "sender 239.255.43.21 45454 \"Hello Multicast!\""; return 1; } QString mode = args[1]; QString multicastGroup = args[2]; quint16 port = args[3].toUShort(); QString message = (args.size() > 4) ? args[4] : "Default multicast message"; Multicast multicast; if (mode == "receiver") { multicast.startReceiver(multicastGroup, port); } else if (mode == "sender") { multicast.startSender(multicastGroup, port, message); } else { qWarning() << "Invalid mode:" << mode; return 1; } // 退出计时器(仅用于演示) QTimer::singleShot(30000, &a, SLOT(quit())); return a.exec(); } ``` #### `.pro` 项目文件 ```qmake QT += core network TARGET = multicast_example TEMPLATE = app CONFIG += console CONFIG -= app_bundle SOURCES += main.cpp \ multicast.cpp HEADERS += multicast.h ``` ### 编译与运行 1. **编译程序**: ```bash qmake-qt4 make ``` 2. **启动接收端**: ```bash ./multicast_example receiver 239.255.43.21 45454 ``` 3. **启动发送端** (在另一个终端): ```bash ./multicast_example sender 239.255.43.21 45454 "Hello from Qt4 multicast!" ``` ### 关键功能说明 1. **地址选择**: - 使用 `239.255.43.21` 作为示例地址(范围 224.0.0.0 到 239.255.255.255) - 避免使用 224.0.0.0-224.0.0.255(保留地址) 2. **网络接口选择**: ```cpp QList<QNetworkInterface> interfaces = QNetworkInterface::allInterfaces(); foreach (const QNetworkInterface &interface, interfaces) { if (interface.flags() & QNetworkInterface::CanMulticast) { // 使用支持的接口 } } ``` 3. **TTL (Time To Live) 设置**: ```cpp int ttl = 1; // 限制在本地网络 setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)); ``` 4. **指定输出接口**: ```cpp struct in_addr ifaceAddr; ifaceAddr.s_addr = htonl(addr.toIPv4Address()); setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_IF, &ifaceAddr, sizeof(ifaceAddr)); ``` ### 常见问题解决 1. **"joinMulticastGroup failed" 错误**: - 确保网络接口支持(`ifconfig` 查看) - 检查防火墙设置:`sudo ufw allow 45454/udp` - 尝试绑定到特定接口: ```cpp m_socket->joinMulticastGroup(groupAddress, QNetworkInterface::interfaceFromName("eth0")); ``` 2. **接收不到数据**: - 验证路由:`sudo route add -net 239.255.43.21 netmask 255.255.255.255 dev eth0` - 使用 `tcpdump` 调试: ```bash sudo tcpdump -i eth0 -n udp port 45454 ``` 3. **IPv6 支持**: ```cpp // 对于IPv6 QHostAddress groupAddress("ff02::1"); // 所有节点的本地链路范围 setsockopt(sockfd, IPPROTO_IPV6, IPV6_MULTICAST_IF, ...); ``` ### 地址范围参考 | 地址范围 | 用途 | |-------------------------|--------------------------| | 224.0.0.0 - 224.0.0.255 | 本地网络控制(保留) | | 224.0.1.0 - 224.0.1.255 | 互联网控制 | | 232.0.0.0 - 232.255.255.255 | 源特定 (SSM) | | 233.0.0.0 - 233.255.255.255 | GLOP 地址(AS号映射) | | 239.0.0.0 - 239.255.255.255 | 管理范围 |
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