udp.zip_udp socket message

/****************************************************************************************\ * *\ * *\ * program name:udpserver.c *\ * Author: Liang gang & Hu xiao-qin *\ * Funtion:tell students how to use SOCK_DGRAM toimplment a commuantion program *\ * Date:10-03-2009 *\ * *\ *****************************************************************************************/ #include<stdlib.h> #include<stdio.h> #include<string.h> #include<sys/types.h> #include<sys/socket.h> #include<netinet/in.h> #include<netdb.h> #define PORT 8900 int main() { int sockfd; struct sockaddr_in server; struct sockaddr_in client; char send_buf[2048]; char recv_buf[2048]; int length; int sendnum; int recvnum; int port; port = PORT; int opt = SO_REUSEADDR; /*The first stage:initnial phase*/ /*1.1 generating socket phrahse*/ if (-1==(sockfd=socket(AF_INET,SOCK_DGRAM,0))) { perror("error in generate socket\n"); exit(1); } #ifdef DEBUG printf("the sokcet id is %d\n",sockfd); printf("enter binding phrase....\n"); #endif setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt)); /*1.2 binding the socket*/ memset(&server,0,sizeof(struct sockaddr)); server.sin_family = AF_INET; server.sin_addr.s_addr = htonl(INADDR_ANY); server.sin_port = htons(port); if (-1==bind(sockfd,(struct sockaddr*)&server,sizeof(struct sockaddr))) { perror("error in binding phrase\n"); close(sockfd); exit(1); } #ifdef DEBUG printf("leaving binding phrase\n"); printf("entering data exchange phrase\n"); #endif length = sizeof(struct sockaddr_in); /* The Second Stage: data exchange phrase */ while(1) { memset(&send_buf,0,sizeof(send_buf)); memset(&recv_buf,0,sizeof(recv_buf)); /* receive the data from the client*/ recvnum=recvfrom(sockfd,recv_buf,sizeof(recv_buf),0,(struct sockaddr*)&client,&length); recv_buf[recvnum]='\0'; printf("the message from the client is %s:\n",recv_buf); sendnum = sprintf(send_buf,"hello,the guest from %s",inet_ntoa(client.sin_addr)); sendto(sockfd,send_buf,sendnum,0,(struct sockaddr*)&client,sizeof(struct sockaddr)); if (0==strcmp(recv_buf,"quit")) { perror("the server is terminted by client\n"); close(sockfd); return 0; } } }