因为不能通过socket找到对方, 只要是udp发消息, 就得通过sendto()
server clientTCP/IP send();recv() send();recv()
UDP/IP recvfrom();sendto() recv();sendto()
例子-一对一的upd/ip协议的服务器模型 //udp/ip server 五步走 #include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #include<arpa/inet.h> int main(){ //1. 创建socket int sockfd=socket(AF_INET,SOCK_DGRAM,0); if(-1==sockfd) perror("socket"),exit(-1); //2. 准备通信地址 struct sockaddr_in addr; addr.sin_family=AF_INET; addr.sin_port=htons(8888); addr.sin_addr.s_addr=inet_addr("176.43.11.211"); //3. 绑定socket和通信地址 int res=bind(sockfd,(struct sockaddr*)&addr,sizeof(addr)); if(-1==res) perror("bind"),exit(-1); printf("bind success\n"); //4. 进行通信 char buf[100]={0}; struct sockaddr_in recv_addr; //为使用recvfrom得到client地址做准备, 最终为sendto()做准备 socklen_t len=sizeof(recv_addr); res=recvfrom(sockfd,buf,sizeof(buf),0,(struct sockaddr*)&recv_addr,&len); if(-1==res) perror("recvfrom"),exit(-1); char* ip=inet_ntoa(recv_addr.sin_addr); //将recvfrom获得client地址转换成点分十进制字符串 printf("data received from client :%s is:%d\n",ip,res); res=sendto(sockfd,"I received",sizeof("I received"),0,(struct sockaddr*)&recv_addr,len);//使用recvfrom获得的client地址 if(-1==res) perror("sendto"),exit(-1); //5. 关闭socket res=close(sockfd); if(-1==res) perror("close"),exit(-1); printf("close success\n"); return 0; } //udp/ip client #include<stdio.h> #include<stdlib.h> #include<unistd.h> //close() #include<sys/types.h> #include<sys/socket.h> #include<arpa/inet.h> #include<netinet/in.h> int main(){ int sockfd=socket(AF_INET,SOCK_DGRAM,0); if(-1==sockfd) perror("socket"),exit(-1); printf("create socket succesfully\n"); struct sockaddr_in addr; addr.sin_family=AF_INET; addr.sin_port=htons(8888); addr.sin_addr.s_addr=inet_addr("176.43.11.211"); //这个是server的地址, 虽然没有connect, which means 不能通过socket找到这个地址, 但是我们还是知道这个地址的, sendto()是可以直接用的 int res=sendto(sockfd,"hello",sizeof("hello"),0,(struct sockaddr*)&addr,sizeof(addr)); if(-1==res) perror("sendto"),exit(-1); printf("data sent size:%d\n",res); char buf[100]={0}; res=recv(sockfd,buf,sizeof(buf),0); if(-1==res) perror("recv"),exit(-1); printf("data received from server:%s\n",buf); res=close(sockfd); if(-1==res) perror("close"),exit(-1); return 0; }