linux UDP 局域网内广播通信服务器端和客户端

在调试局域网内通过UDP协议获取其他设备IP地址时,服务器使用UDP 广播后, 客户端设备无响应. 先研究一下正常情况下, UDP广播通信方法. 参考了网络上一写资料. 代码整理如下:

服务器端向: 255.255.255.255:6023发送UDP广播:

serverUDP.c

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#define PORT 6023

int main()

{

setvbuf(stdout, NULL, _IONBF, 0);

fflush(stdout);



int sock = -1;

if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)

{

printf("socket error\n");

return -1;

}



const int opt = 1;

//设置该套接字为广播类型，

int nb = 0;

nb = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char *)&opt, sizeof(opt));

if(nb == -1)

{

printf("set socket error...\n");

return -1;

}



struct sockaddr_in addrto;

bzero(&addrto, sizeof(struct sockaddr_in));

addrto.sin_family=AF_INET;

addrto.sin_addr.s_addr=htonl(INADDR_BROADCAST);

addrto.sin_port=htons(PORT);

int nlen=sizeof(addrto);



while(1)

{

sleep(1);

//从广播地址发送消息

char smsg[] = {"abcdef"};

int ret=sendto(sock, smsg, strlen(smsg), 0, (struct sockaddr*)&addrto, nlen);

if(ret<0)

{

printf("send error....\n");

}

else

{

printf("ok \n");

}

}



return 0;

}

客户端接收广播消息.

clientUDP.c

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <errno.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>



#define PORT 6023

int main()

{

setvbuf(stdout, NULL, _IONBF, 0);

fflush(stdout);



// 绑定地址

struct sockaddr_in addrto;

bzero(&addrto, sizeof(struct sockaddr_in));

addrto.sin_family = AF_INET;

addrto.sin_addr.s_addr = htonl(INADDR_ANY);

addrto.sin_port = htons(PORT);



// 广播地址

struct sockaddr_in from;

bzero(&from, sizeof(struct sockaddr_in));

from.sin_family = AF_INET;

from.sin_addr.s_addr = htonl(INADDR_ANY);

from.sin_port = htons(PORT);



int sock = -1;

if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)

{

printf("socket error\n");

return -1;

}



const int opt = 1;

//设置该套接字为广播类型，

int nb = 0;

nb = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (char *)&opt, sizeof(opt));

if(nb == -1)

{

printf("set socket error...\n");

return -1;

}



if(bind(sock,(struct sockaddr *)&(addrto), sizeof(struct sockaddr_in)) == -1)

{

printf("bind error...\n");

return -1;

}



int len = sizeof(struct sockaddr_in);

char smsg[100] = {0};



while(1)

{

//从广播地址接受消息

int ret=recvfrom(sock, smsg, 100, 0, (struct sockaddr*)&from,(socklen_t*)&len);

if(ret<=0)

{

printf("read error....\n");

}

else

{

printf("%s\t", smsg);

}



sleep(1);

}



return 0;

}

Makefile:

all: server client

server:

gcc serverUDP.c -o serverUDP

client:

gcc clientUDP.c -o clientUDP

clean:

rm serverUDP clientUDP

如局域网内有A设备, IP为192.168.1.100, B设备, IP为192.168.1.101.

在A设备上运行 ./clientUDP &

在B设备上运行 ./serverUDP &

运行结果:

A设备上一直打印: abcdef

B设备上一直打印: ok.