수다닷컴

예제를 그대로쳐서해봣는데 컴파일은 되는데 ... 자꾸 recvfrom 이함수부분에서 엉키는거같더라구요 ㅜㅜ
멀티캐스트를이용한 채팅프로그램입니다 ㅜ ㅜ어디가문제일까요
#include stdio.h
#include sys/types.h
#include sys/socket.h
#include netinet/in.h
#include arpa/inet.h
#include stdlib.h
#include unistd.h
#include string.h
char *msg_exit = exit\n;
#define MAXLINE 1024
int main(int argc, char **argv)
{
int read_fd;
int send_fd;
pid_t pid;
int flag;
struct sockaddr_in from;
int addrlen;
struct sockaddr_in mcast_group;
struct ip_mreq mreq;
char name[16];
char message[MAXLINE];
if(argc != 4){
printf(Usage : %s\n, argv[0]);
return 1;
}
sprintf(name, %s, argv[3]);
memset(&mcast_group, 0x00, sizeof(mcast_group));
mcast_group.sin_family=AF_INET;
mcast_group.sin_port=htons(atoi(argv[2]));
inet_pton(AF_INET, argv[1], &mcast_group.sin_addr);
if( (read_fd = socket(AF_INET, SOCK_DGRAM, 0 )) 0 )
{
return 1;
mreq.imr_multiaddr = mcast_group.sin_addr;
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
if(setsockopt(read_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,
sizeof(mreq)) 0){
perror(error: add group\n);
return 1;
}
flag=1;
if(setsockopt(read_fd, SOL_SOCKET, SO_REUSEADDR, &flag,
sizeof(flag)) 0)
{
printf(Socket Reuseaddr erro\n);
return 1;
}
if(bind(read_fd, (struct sockaddr *)&mcast_group,
sizeof(mcast_group)) 0){
return 1;
}
if( (send_fd = socket(AF_INET, SOCK_DGRAM, 0)) 0)
{
return 1;
}
pid=fork();
if(pid 0)
{
printf(for error\n);
return 1;
}
else if(pid == 0)
{
while(1)
{
addrlen=sizeof(from);
memset(message, 0x00, sizeof(message));
if(readn=recvfrom(read_fd, message, MAXLINE, 0,
(struct sockaddr*)&from, &addrlen) 0)
{
perror(recvfrom:);
return 1;
}

printf(%s, message);
if(strstr(message, msg_exit) != NULL)
{
printf(EXIT\n);
if(setsockopt(read_fd, IPPROTO_IP, IP_DROP_MEMBERSHIP,
&mreq, sizeof(mreq)) 0)
{
return 1;
}
}
}
}
else
{
while(1)
{
memset(message, 0x00, MAXLINE);
read(0, message, MAXLINE);
sprintf(message, %s : %s, name, message);
if(sendto(send_fd, message, strlen(message), 0,
(struct sockaddr *)&mcast_group,
&; sizeof(mcast_group)) strlen(message))
{
return 1;
}
}
}
return 0;
}

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