我正在编写多播环境场景。源正在将内容发送到多播地址，例如239.0.1.1。另一方面，客户端想要加入此多播地址。组播的实际工作是希望加入组播组的客户端向其连接的路由器发送加入请求。我必须对从客户端接收多播加入请求的路由器操作进行编程，从多播地址获取数据并将内容提供给客户。我无法弄清楚如何做到这一点。对于单个用户来说很好。但是当有多个客户端时，我使用的技术不正确...请帮助我..加入特定地址并将数据发送到单个客户端的代码如下所示：
#include <sys/types.h> /* for type definitions */
#include <sys/socket.h> /* for socket API calls */
#include <netinet/in.h> /* for address structs */
#include <arpa/inet.h> /* for sockaddr_in */
#include <stdio.h> /* for printf() and fprintf() */
#include <stdlib.h> /* for atoi() */
#include <string.h> /* for strlen() */
#include <unistd.h> /* for close() */
#define MAX_LEN 4074 /* maximum receive string size */
#define MIN_PORT 1024 /* minimum port allowed */
#define MAX_PORT 65535 /* maximum port allowed */
int main(int argc, char *argv[])
{
int sock; /* socket descriptor */
int flag_on = 1; /* socket option flag */
struct sockaddr_in mc_addr; /* socket address structure */
char recv_str[MAX_LEN+1]; /* buffer to receive string */
int recv_len; /* length of string received */
struct ip_mreq mc_req; /* multicast request structure */
char* mc_addr_str; /* multicast IP address */
unsigned short mc_port; /* multicast port */
//unsigned short mc_port1=1400; /*multicast port */
struct sockaddr_in from_addr; /* packet source */
unsigned int from_len; /* source addr length */
// to send the data to the client
int sockfd, newsockfd, portno;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
int n;
int cnt;
int no=4096,i;
char *buffer[no];
int dest_sock;
struct sockaddr_in dest_addr;
char * dest_address="192.168.1.4";
unsigned int dest_port=5000;
/* validate number of arguments */
if (argc != 3)
{
fprintf(stderr,
"Usage: %s <Multicast IP> <Multicast Port>\n",
argv[0]);
exit(1);
}
mc_addr_str = argv[1]; /* arg 1: mlticast ip address */
mc_port = atoi(argv[2]); /* arg 2: multicast port number */
/* validate the port range */
if ((mc_port < MIN_PORT) || (mc_port > MAX_PORT)) {
fprintf(stderr, "Invalid port number argument %d.\n",
mc_port);
fprintf(stderr, "Valid range is between %d and %d.\n",
MIN_PORT, MAX_PORT);
exit(1);
}
/* create socket to join multicast group on */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
perror("socket() failed");
exit(1);
}
else
printf("Socket connection successful\n");
/* set reuse port to on to allow multiple binds per host */
if ((setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &flag_on,
sizeof(flag_on))) < 0) {
perror("setsockopt() failed");
exit(1);
}
/* construct a multicast address structure */
memset(&mc_addr, 0, sizeof(mc_addr));
mc_addr.sin_family = AF_INET;
mc_addr.sin_addr.s_addr = htonl(INADDR_ANY);
mc_addr.sin_port = htons(mc_port);
/* bind to multicast address to socket */
if ((bind(sock, (struct sockaddr *) &mc_addr,
sizeof(mc_addr))) < 0) {
perror("bind() failed");
exit(1);
}
/* construct an IGMP join request structure */
mc_req.imr_multiaddr.s_addr = inet_addr(mc_addr_str);
mc_req.imr_interface.s_addr = htonl(INADDR_ANY);
/* send an ADD MEMBERSHIP message via setsockopt */
if ((setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
(void*) &mc_req, sizeof(mc_req))) < 0) {
perror("setsockopt() failed");
exit(1);
}
printf("setsocket successfull\n");
//for sending the data to the client
//creating a socket to the client and waiting for the client to receive the data
if ((dest_sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
perror("socket() failed");
exit(1);
}
else
printf("Socket connection successful\n");
if ((setsockopt(dest_sock, SOL_SOCKET, SO_REUSEADDR, &flag_on,
sizeof(flag_on))) < 0) {
perror("setsockopt() failed");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = 5000;//atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr,
// sizeof(serv_addr)) < 0)
// error("ERROR on binding");
// listen(sockfd,5);
// clilen = sizeof(cli_addr);
// newsockfd = accept(sockfd,
//(struct sockaddr *) &cli_addr,
// // &clilen);
//if (newsockfd < 0)
// error("ERROR on accept");
/*------------------------------------------------------------------------------------------------------*/
for(cnt=0;cnt<100;cnt++) { /* loop forever */
/* clear the receive buffers & structs */
memset(recv_str, 0, sizeof(recv_str));
from_len = sizeof(from_addr);
memset(&from_addr, 0, from_len);
/* block waiting to receive a packet */
//buffer[cnt]=recvfrom(sock, recv_str, MAX_LEN, 0,(struct sockaddr*)&from_addr, &from_len);
// no++;
if ((recv_len = recvfrom(sock, recv_str, MAX_LEN, 0,(struct sockaddr*)&from_addr, &from_len)) < 0)
//if(strlen(buffer[cnt])<0)
{
perror("recvfrom() failed");
exit(1);
}
/* output received string */
// printf("Received %d bytes from %s: ", recv_len, inet_ntoa(from_addr.sin_addr));
printf("\n");
//printf("%s\n",recv_str);
//printf("\n");
//buffer[i]=recv_str;
//printf("%s\n",buffer[i]);
//printf("Enter the writing mode\n");
n = write(newsockfd,recv_str,sizeof(recv_str));
i++;
//printf("%d\n",n);
if (n < 0)
{
error("ERROR writing to socket");
exit(1);
}
i++;
//return 0;
}
close(newsockfd);
close(sockfd);
/* send a DROP MEMBERSHIP message via setsockopt */
if ((setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
(void*) &mc_req, sizeof(mc_req))) < 0) {
perror("setsockopt() failed");
exit(1);
}
close(sock);
}