LINUX C++ 廣播程式[LINUX_CPP_Broadcast]

資料來源: http://chriswenyuan.blogspot.com/2017/05/c-broadcast.html

Server 端程式

/* broadcast_server.c */
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <unistd.h>

/*Set port number*/
#define PORT 8888

int main(){
 int sockfd;
 struct sockaddr_in server_addr, client_addr;
 int so_broadcast = 1;
 char buf[1024];

 /*Create an IPv4 UDP socket*/
 if((sockfd = socket(PF_INET, SOCK_DGRAM, 0))<0){
  perror("socket");
  return -1;
 }

 /*SO_BROADCAST: broadcast attribute*/
 if(setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &so_broadcast, sizeof(so_broadcast))<0){
  perror("setsockopt");
  return -1;
 }

 server_addr.sin_family = AF_INET; /*IPv4*/
 server_addr.sin_port = htons(INADDR_ANY); /*All the port*/
 server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); /*Broadcast address*/

 if((bind(sockfd, (struct sockaddr*)&server_addr, sizeof(struct sockaddr))) != 0){
  perror("bind");
  return -1;
 }

 client_addr.sin_family = AF_INET; /*IPv4*/
 client_addr.sin_port = htons(PORT);  /*Set port number*/
 client_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); /*The broadcast address*/
 int clientlen = sizeof(client_addr);

 while(1){
  printf("Please input your word :> ");
  //scanf("%s", buf);
  fgets(buf, sizeof(buf), stdin); /*U can enter string by yourself*/

  /*Use sendto() to send messages to client*/
  /*sendto() doesn't need to be connected*/
  if((sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr*)&client_addr, (socklen_t)clientlen)) < 0){
   perror("sendto");
   return -1;
  } 

  else
   printf("send msg %s\n", buf);
 }

 close(sockfd);
 return 0;
}

Client 端程式

#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <unistd.h>

#define PORT 8888

int main(){
 int sockfd;
 struct sockaddr_in serv_addr, client_addr;
 int yes = 1;
 ssize_t size;
 socklen_t addrlen = sizeof(client_addr);
 char buf[200];

 //Create an IPv4 and UDP socket
 if((sockfd = socket(PF_INET, SOCK_DGRAM, 0))<0){
  perror("socket");
  return -1;
 }

 //Set the struct of sockaddr_in
 serv_addr.sin_family = AF_INET;
 serv_addr.sin_port = htons(PORT);
 serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); /*All the host*/

 /*Set communication address can be reused*/
 if(setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes))<0){
  perror("setsockopt");
  return -1;
 }

 if(bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) != 0){
  perror("bind");
  return -1;
 }

 while(1){
  memset(buf, 0, 200); /*Clean up the buffer*/
  size = 0;

  /*Use recvfrom() to receive the messages from server*/
  size = recvfrom(sockfd, buf, 200, 0, (struct sockaddr *)&client_addr, &addrlen);
  if(size<0){
   perror("recvfrom");
   return -1;
  }

  //buf[size] = '\0'; /* '\0' means final character*/

  printf("IP:%s msg: %s\n", inet_ntoa(client_addr.sin_addr), buf);

  /*If the buffer message is "quit", we will close socket fd and end the process*/
  if(strcmp(buf, "quit") == 0){
   printf("system quit!\n");
   close(sockfd);
   return 0;
  }
 }

 close(sockfd);
 return 0;
}