linux socket UDP编程发送广播

#include<stdio.h>

#include<stdlib.h>

#include<errno.h>

#include<string.h>

#include<sys/types.h>

#include<netinet/in.h>

#include<sys/socket.h>

#include<sys/wait.h>

#include<sys/stat.h>

#include<fcntl.h>

#include<unistd.h>

#include
<arpa/inet.h>

#include<netdb.h>

#define PORT
7773

#define
MAXDATASIZE 256

int main(int
argc,char *argv[])

{

int socket_fd;

struct sockaddr_in my_addr,user_addr;

char buf[MAXDATASIZE];

int so_broadcast=1;

socklen_t size;

char my_ip[12];

my_addr.sin_family=AF_INET;

my_addr.sin_port=htons(PORT);

my_addr.sin_addr.s_addr=inet_addr("255.255.255.255");

bzero(&(my_addr.sin_zero),8);

user_addr.sin_family=AF_INET;

user_addr.sin_port=htons(PORT);

user_addr.sin_addr.s_addr=htonl(INADDR_ANY);

bzero(&(user_addr.sin_zero),8);

if((socket_fd=(socket(AF_INET,SOCK_DGRAM,0)))==-1)
{

perror("socket");

exit(1);

}

setsockopt(socket_fd,SOL_SOCKET,SO_BROADCAST,&so_broadcast,sizeof(so_broadcast));

if((bind(socket_fd,(struct sockaddr
*)&user_addr,

sizeof(struct sockaddr)))==-1) {

perror("bind");

exit(1);

}

strcpy(buf,"Hello,I'm on
line!");

sendto(socket_fd,buf,strlen(buf),0,(struct
sockaddr *)&my_addr,sizeof(my_addr));

size=sizeof(user_addr);

recvfrom(socket_fd,buf,MAXDATASIZE,0,(struct
sockaddr *)&user_addr,&size);

strcpy(my_ip,inet_ntoa(user_addr.sin_addr));

printf("my_ip:%sn",inet_ntoa(user_addr.sin_addr));

while(1) {

bzero(buf, sizeof(buf));

size=sizeof(user_addr);

recvfrom(socket_fd,buf,MAXDATASIZE,0,(struct
sockaddr *)&user_addr,&size);

printf("%s:%sn",inet_ntoa(user_addr.sin_addr),buf);

bzero(buf, sizeof(buf));

if(strcmp(buf,"I'm off line,bye!")==0)

strcpy(buf,"ok,I
know,bye!");

else {

strcpy(buf,"send,Hello,I get
you!");

sleep(1);

}

if((sendto(socket_fd,buf,strlen(buf),0,

(struct sockaddr *)&user_addr,sizeof(user_addr)))==-1)

perror("sendto");

}

return 0;

}

执行：

gcc -o udp
udp.c

./udp