组播收发的程序
发送方：
#include <sys/types.h> /* for type definitions */
#include <sys/socket.h> /* for socket API function calls */
#include <netinet/in.h> /* for address structs */
#include <arpa/inet.h> /* for sockaddr_in */
#include <stdio.h> /* for printf() */
#include <stdlib.h> /* for atoi() */
#include <string.h> /* for strlen() */
#include <unistd.h> /* for close() */
#define MAX_LEN 1024 /* maximum string size to send */
#define MIN_PORT 1024 /* minimum port allowed */
#define MAX_PORT 65535 /* maximum port allowed */
int main(int argc, char *argv[])
{
int sock; /* socket descriptor */
char send_str[MAX_LEN]; /* string to send */
struct sockaddr_in mc_addr; /* socket address structure */
unsigned int send_len; /* length of string to send */
char* mc_addr_str; /* multicast IP address */
unsigned short mc_port; /* multicast port */
unsigned char mc_ttl=1; /* time to live (hop count) */
/* 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: multicast 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 a socket for sending to the multicast address */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
{
perror("socket() failed");
exit(1);
}
/* set the TTL (time to live/hop count) for the send */
if ((setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (void*) &mc_ttl, sizeof(mc_ttl))) < 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 = inet_addr(mc_addr_str);
mc_addr.sin_port = htons(mc_port);
printf("Begin typing (return to send, ctrl-C to quit):\n");
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
while (fgets(send_str, MAX_LEN, stdin))
{
send_len = strlen(send_str);
/* send string to multicast address */
if ((sendto(sock, send_str, send_len, 0, (struct sockaddr *) &mc_addr, sizeof(mc_addr))) != send_len)
{
perror("sendto() sent incorrect number of bytes");
exit(1);
}
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
}
close(sock);
exit(0);
}
接收方：
#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 1024 /* 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 */
struct sockaddr_in from_addr; /* packet source */
unsigned int from_len; /* source addr length */
/* 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: multicast 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);
}
/* 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);
}
for (;;)
{ /* 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 */
if ((recv_len = recvfrom(sock, recv_str, MAX_LEN, 0, (struct sockaddr*)&from_addr, &from_len)) < 0)
{
perror("recvfrom() failed");
exit(1);
}
/* output received string */
printf("Received %d bytes from %s: ", recv_len, inet_ntoa(from_addr.sin_addr));
printf("%s", recv_str);
}
/* 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);
}