c++ udp组播总结
概念
多播，也称为“组播”，将网络中同一业务类型主机进行了逻辑上的分组，进行数据收发的时候其数据仅仅在同一分组中进行，其他的主机没有加入此分组不能收发对应的数据。
特点
- 优点
- 具有同种业务的主机加入同一数据流，共享同一通道，节省了带宽；
- 服务器的总带宽不受客户端带宽的限制，服务器端的带宽是常量，与客户端的数量无关；
- 允许在广域网传输；
- 缺点
- 没有纠错机制；
- 需要路由器和网络协议栈的支持；
流程
-
发送端
- 创建socket；
// 第二个参数是 SOCK_DGRAM, 第三个参数0表示使用报式协议中的udp int socketFd = socket(AF_INET, SOCK_DGRAM, 0); if(-1 == socketFd) { printf("create udp socket failed\n"); return -1; }- bind（可选）
// 使用场景: 使用同一个socketFD接收消息(即recvfrom) // 说明: 一般将addr.sin_addr.s_addr设置为本机网卡地址 struct sockaddr_in cliaddr; cliaddr.sin_family = AF_INET; cliaddr.sin_port = htons(18001); cliaddr.sin_addr.s_addr = INADDR_ANY; // ???本地ip int ret = bind(socketFd, (struct sockaddr*)&cliaddr, sizeof(cliaddr)); if(ret == -1) { printf("udp bind failed\n"); return -1; }- 加入组播
// 加入到组播 struct ip_mreqn opt; opt.imr_address.s_addr = htonl(INADDR_ANY); inet_pton(AF_INET, "224.0.2.23", &opt.imr_multiaddr.s_addr); setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &opt, sizeof(opt));扩展：
1）多播使用的是D类ip地址，即224.0.0.0至239.255.255.255之间的ip地址，并被划分为局部多播地址、预留多播地址和管理权限多播地址3类；
1) 局部多播地址: 在224.0.0.0～224.0.0.255之间，这是为路由协议和其他用途保留的地址，路由器并不转发属于此范围的IP包。 2) 预留多播地址: 在224.0.1.0～238.255.255.255之间，可用于全球范围（如Internet）或网络协议。 3) 管理权限多播地址: 在239.0.0.0～239.255.255.255之间，可供组织内部使用，类似于私有IP地址，不能用于Internet，可限制多播范围。2）组播的选项值：
**getsockopt()/setsockopt()**的选项 含义 IP_MULTICAST_TTL 设置多播组数据的TTL值 IP_ADD_MEMBERSHIP 在指定接口上加入组播组 IP_DROP_MEMBERSHIP 退出多播组 IP_MULTICAST_IF 获取默认接口或设置接口 IP_MULTICAST_LOOP 禁止组播数据回送 - 发送数据
char buf[128] = {0,}; snprintf(buf, sizeof(buf), "Get cpu state,i am %d", sessionKey); // 发送数据 sendto(socketFd, buf, strlen(buf)+1, 0, (struct sockaddr*)&cliaddr, sizeof(cliaddr));- 接收数据（如果设置了bind可直接通过socketFd接收数据）
char buf[128] = {0,}; struct sockaddr_in sinAddr; socklen_t addrlen = sizeof(sinAddr); recvfrom(socketFd, buf, sizeof(buf), 0, (struct sockaddr*)&sinAddr, &addrlen); -
接收端
- 创建socket
int socketFd = socket(AF_INET, SOCK_DGRAM, 0); if(-1 == socketFd) { printf("create udp socket failed\n"); return -1; }- bind（必须）
struct sockaddr_in serveraddr; serveraddr.sin_family = AF_INET; serveraddr.sin_port = htons(18000); serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); int ret = bind(fd, (struct sockaddr*)&serveraddr, sizeof(serveraddr)); if(-1 == ret) { printf("udp bind failed\n"); return -1; }- 加入组播
struct ip_mreqn opt; opt.imr_address.s_addr = htonl(INADDR_ANY); inet_pton(AF_INET, "224.0.2.23", &opt.imr_multiaddr.s_addr); setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &opt, sizeof(opt));- 接收数据
char buf[128] = {0,}; struct sockaddr_in sinAddr; socklen_t addrlen = sizeof(sinAddr); recvfrom(socketFd, buf, sizeof(buf), 0, (struct sockaddr*)&sinAddr, &addrlen);- 发送数据
char buf[128] = {0,}; snprintf(buf, sizeof(buf), "Send cpu state,i am %d", sessionKey); // 发送数据 sendto(socketFd, buf, strlen(buf)+1, 0, (struct sockaddr*)&serveraddr, sizeof(serveraddr));
示例
- 接收端
#include
#include
#include
#include
#include
#include
#define TIMEOUT 0xFFFFFFFF
int main()
{
// 1. create socket
int socketFd = socket(AF_INET, SOCK_DGRAM, 0);
if(-1 == socketFd)
{
printf("create udp socket failed\n");
return -1;
}
// 2. bind
struct sockaddr_in serveraddr;
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(18000);
serveraddr.sin_addr.s_addr = INADDR_ANY;
int ret = bind(socketFd, (struct sockaddr*)&serveraddr, sizeof(serveraddr));
if(-1 == ret)
{
printf("udp bind failed\n");
return -1;
}
// 3. set param
// 3.1 ttl
int ttl = 64;
setsockopt(socketFd, IPPROTO_IP, IP_MULTICAST_TTL, (char*)&ttl, sizeof(ttl));
// 3.2 timeout
unsigned int timeout = 2000;
struct timeval tm;
if(TIMEOUT == timeout)
{
tm.tv_sec = 0x7FFFFFFF;
tm.tv_usec = 0;
}
else
{
tm.tv_sec = (timeout&0x7FFFFFFF) / 1000;
tm.tv_usec = (timeout&0x7FFFFFFF) % 1000 * 1000;
}
setsockopt(socketFd, SOL_SOCKET, SO_RCVTIMEO, (char*)&tm, sizeof(tm));
// 4. join multi
struct ip_mreqn opt;
opt.imr_address.s_addr = INADDR_ANY; // 本地地址
inet_pton(AF_INET, "224.0.2.23", &opt.imr_multiaddr.s_addr);
setsockopt(socketFd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &opt, sizeof(opt));
// 5. recvfrom and sendto
while(1)
{
char recv_buf[128] = {0,};
int recvlen = recvfrom(socketFd, recv_buf, sizeof(recv_buf), 0, NULL, NULL);
if(recvlen < 0)
{
//printf("server not recv msg,wait...\n");
continue;
}
printf("server recv msg:%s\n", recv_buf);
sleep(4);
/*
char send_buf[128] = {0,};
snprintf(send_buf, sizeof(send_buf), "Send cpu state,i am %d", 1);
sendto(socketFd, send_buf, sizeof(send_buf), 0, (struct sockaddr*)&serveraddr, sizeof(serveraddr));
printf("server send msg:%s\n", send_buf);
*/
}
return 0;
}
接收端程序运行时打印：
[root@localhost debug.x64-linux-g8]# ./testUdpServer
server recv msg:Send cpu state,i am 1
server recv msg:Send cpu state,i am 1
server recv msg:Send cpu state,i am 1
server recv msg:Send cpu state,i am 1
server recv msg:Send cpu state,i am 1
server recv msg:Send cpu state,i am 1
- 发送端
#include
#include
#include
#include
#include
#include
#define TIMEOUT 0xFFFFFFFF
int main()
{
// 1. create socket
int socketFd = socket(AF_INET, SOCK_DGRAM, 0);
if(-1 == socketFd)
{
printf("create udp socket failed\n");
return -1;
}
// 2. bind
/*
struct sockaddr_in clientaddr;
clientaddr.sin_family = AF_INET;
clientaddr.sin_port = htons(18001);
clientaddr.sin_addr.s_addr = INADDR_ANY;
int ret = bind(socketFd, (struct sockaddr*)&clientaddr, sizeof(clientaddr));
if(-1 == ret)
{
printf("udp bind failed\n");
return -1;
}
*/
// 3. set param
// 3.1 ttl
int ttl = 64;
setsockopt(socketFd, IPPROTO_IP, IP_MULTICAST_TTL, (char*)&ttl, sizeof(ttl));
// 3.2 timeout
unsigned int timeout = 2000;
struct timeval tm;
if(TIMEOUT == timeout)
{
tm.tv_sec = 0x7FFFFFFF;
tm.tv_usec = 0;
}
else
{
tm.tv_sec = (timeout&0x7FFFFFFF) / 1000;
tm.tv_usec = (timeout&0x7FFFFFFF) % 1000 * 1000;
}
setsockopt(socketFd, SOL_SOCKET, SO_RCVTIMEO, (char*)&tm, sizeof(tm));
// 4. set IP_MULTICAST_IF
struct in_addr opt;
inet_pton(AF_INET, "224.0.2.23", &opt.s_addr);
setsockopt(socketFd, IPPROTO_IP, IP_MULTICAST_IF, &opt, sizeof(opt));
struct sockaddr_in clientaddr;
clientaddr.sin_family = AF_INET;
clientaddr.sin_port = htons(18000);
inet_pton(AF_INET, "224.0.2.23", &clientaddr.sin_addr.s_addr);
// 5. recvfrom and sendto
while(1)
{
char send_buf[128] = {0,};
snprintf(send_buf, sizeof(send_buf), "Send cpu state,i am %d", 1);
sendto(socketFd, send_buf, sizeof(send_buf), 0, (struct sockaddr*)&clientaddr, sizeof(clientaddr));
printf("client send msg:%s\n", send_buf);
sleep(2);
/*
char recv_buf[128] = {0,};
struct sockaddr_in sinAddr;
socklen_t addrlen = sizeof(sinAddr);
int recvlen = recvfrom(socketFd, recv_buf, sizeof(recv_buf), 0, (struct sockaddr*)&sinAddr, &addrlen);
if(recvlen < 0)
{
printf("client not recv msg,wait...\n");
continue;
}
printf("client recv msg:%s\n", recv_buf);
*/
}
return 0;
}
发送端程序运行时打印：
[root@localhost debug.x64-linux-g8]# ./testUdpClient
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1
client send msg:Send cpu state,i am 1