C语言socket UDP广播的发送和接收示例
server.c通过UDP广播的形式向网段的指定端口发送广播信息
client.c绑定到指定端口，并阻塞接收广播内容然后打印出来 程序非常简单，不过有一点需要注意，那就是setsockopt()函数的使用。使用不当很可能会出问题。通过SO_REUSEADDR选项可以实现端口号的重用，
SO_BROADCAST选项表示要发送的是广播信息，optval参数要给合理的初始值（这里是1），否则很可能会发送失败 (sendto() permission denied)
发送广播的程序：[cpp] view plaincopy#include<stdio.h> #include<stdlib.h> #include<string.h> #include<sys/types.h> #include<sys/socket.h> #include<sys/wait.h> #include<netinet/in.h> #include<arpa/inet.h> #include<errno.h> int main(){ char msg[128] = \server!\ int brdcFd; if((brdcFd = socket(PF_INET,
SOCK_DGRAM, 0)) == -1){ printf(\ return -1; } int optval = 1;//这个值一定要设置，否则可能导致sendto()失败 setsockopt(brdcFd, SOL_SOCKET, SO_BROADCAST | SO_REUSEADDR,
&optval, sizeof(int)); struct sockaddr_in theirAddr; memset(&theirAddr, 0, sizeof(struct sockaddr_in)); theirAddr.sin_family = AF_INET;
theirAddr.sin_addr.s_addr = inet_addr(\ theirAddr.sin_port = htons(4001); int sendBytes; if((sendBytes = sendto(brdcFd, msg, strlen(msg), 0, (struct sockaddr *)&theirAddr, sizeof(struct sockaddr))) == -1){ printf(\ return -1; } printf(\sendBytes=%d\\n\ close(brdcFd); return 0; } 接收程序：[cpp] view plaincopy#include<stdlib.h> #include<stdio.h> #include<string.h> #include<sys/types.h> #include<netinet/in.h> #include<netdb.h> #include<sys/socket.h> #include<sys/wait.h> #include<arpa/inet.h> int main(){ int sockListen; if((sockListen = socket(AF_INET, SOCK_DGRAM, 0)) == -1){ printf(\ return -1; } int set = 1; setsockopt(sockListen, SOL_SOCKET, SO_REUSEADDR, &set, sizeof(int)); struct sockaddr_in recvAddr; memset(&recvAddr, 0, sizeof(struct sockaddr_in)); recvAddr.sin_family =
AF_INET; recvAddr.sin_port = htons(4001); recvAddr.sin_addr.s_addr = INADDR_ANY; // 必须绑定，否则无法监听 if(bind(sockListen, (struct sockaddr *)&recvAddr, sizeof(struct sockaddr)) == -1){ printf(\ return -1; } int recvbytes; char recvbuf[128]; int addrLen = sizeof(struct sockaddr_in); if((recvbytes = recvfrom(sockListen, recvbuf, 128, 0, (struct sockaddr *)&recvAddr, &addrLen)) != -1){ recvbuf[recvbytes] = '\\0'; printf(\recvbuf); }else{ printf(\
fail\\n\ } close(sockListen); return 0; }