#include <sys/types.h> #include <sys/socket.h> #include <string.h> #include <netinet/in.h> #include <stdio.h> #include <stdlib.h> #define MAXLINE 80 #define SERV_PORT 6970 void do_echo(int sockfd, struct sockaddr *pcliaddr, socklen_t clilen) { int n; socklen_t len; char mesg[MAXLINE]; for(;;) { len = clilen; /* waiting for receive data */ n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len); /* sent data back to client */ printf("receieve: %s\n",mesg); fflush ( stdout ) ; sendto(sockfd, mesg, n, 0, pcliaddr, len); } } int main(void) { int sockfd; struct sockaddr_in servaddr, cliaddr; sockfd = socket(AF_INET, SOCK_DGRAM, 0); /* create a socket */ /* init servaddr */ bzero(&servaddr, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(SERV_PORT); /* bind address and port to socket */ if(bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) { perror("bind error"); exit(1); } do_echo(sockfd, (struct sockaddr *)&cliaddr, sizeof(cliaddr)); return 0; }