C语言编译的基于Linux下的client与server的DNS与查询

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <netdb.h> #include <unistd.h> #include <sys/socket.h> #include <netinet/in.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> typedef struct information { char ID[20]; char email[40]; } information; information info[50]; int main( int argc, char *argv[] ) { int sockfd, newsockfd; socklen_t addr_size; struct sockaddr_in serv_addr, cli_addr; struct in_addr **addr_list; FILE *fp; char buffer[256]; struct hostent *hptr; char *IP; int i=0, j=0, k=0,n; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) { perror("ERROR socket"); exit(1); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); serv_addr.sin_port = htons(5343); if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) { perror("ERROR binding"); exit(1); } if(listen(sockfd,10)){ printf(" Listen Failed!"); exit(1); } addr_size = sizeof(cli_addr); while(1) { newsockfd = accept (sockfd, (struct sockaddr *) &cli_addr, &addr_size); fp = fopen("employee.txt","r"); while(!feof(fp)) { fscanf(fp,"%s%s", info[k].ID, info[k].email); k++; } fclose(fp); while(1){ bzero(buffer, 256); n = read(newsockfd,buffer,255); while (buffer[i] < 57 && buffer[i] > 48) i++; if (n == i) { for(j = 0; j < k; j++) { if(!strcmp(info[j].ID, buffer)) { write(newsockfd,info[j].email,strlen(info[j].email)); break; } } if(j==k) write(newsockfd,"query failed",18); } else{ if((hptr = gethostbyname(buffer)) == NULL) exit(1); IP = inet_ntoa(*((struct in_addr *)hptr->h_addr)); write(newsockfd,IP,strlen(IP)); } } } close(newsockfd); return 0; }