linux 网络编程（UDP）

#include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <netinet/in.h> #include <sys/socket.h> #include <sys/wait.h> #define RPORT 5000 //要链接的端口号 #define SPORT 6000 #define MAXBUFLEN 100 //能够接收的最长数据 main() { int sockfd1,sockfd2; struct sockaddr_in my1_addr; struct sockaddr_in my2_addr; struct sockaddr_in sendpc_addr; struct sockaddr_in receivepc_addr; int addr_len,numbytes1,numbytes2,numbytes3; char buf[MAXBUFLEN]; char test[3]; if((sockfd1 = socket(AF_INET,SOCK_DGRAM,0)) == -1) { perror("socket1"); exit(1); } if((sockfd2 = socket(AF_INET,SOCK_DGRAM,0)) == -1) { perror("socket2"); exit(1); } my1_addr.sin_family = AF_INET; my1_addr.sin_port = htons(RPORT); my1_addr.sin_addr.s_addr = INADDR_ANY; bzero(&(my1_addr.sin_zero),8); my2_addr.sin_family = AF_INET; my2_addr.sin_port = htons(SPORT); my2_addr.sin_addr.s_addr = INADDR_ANY; bzero(&(my2_addr.sin_zero),8); if(bind(sockfd1,(struct sockaddr*)&my1_addr,sizeof(struct sockaddr)) == -1) { perror("bind1"); exit(1); } if(bind(sockfd2,(struct sockaddr*)&my2_addr,sizeof(struct sockaddr)) == -1) { perror("bind2"); exit(1); } addr_len = sizeof(struct sockaddr); if((numbytes1 = recvfrom(sockfd1,buf,MAXBUFLEN,0,(struct sockaddr*)&sendpc_addr,&addr_len)) == -1) { perror("recvfrom1"); exit(1); } printf("got packet from %s\n",inet_ntoa(sendpc_addr.sin_addr)); printf("packet is %d bytes long\n",numbytes1); buf[numbytes1] = '\0'; printf("packet contains \"%s\"\n",buf); close(sockfd1); if((numbytes2 = recvfrom(sockfd2,test,3,0,(struct sockaddr*)&receivepc_addr,&addr_len)) == -1) { perror("recvfrom2"); exit(1); } if(test[0]) { printf("*******************************************\n"); if((numbytes3 = sendto(sockfd2,buf,numbytes1,0,(struct sockaddr*)&receivepc_addr,sizeof(struct sockaddr))) == -1); { perror("sendto2"); exit(1); } printf("send %d bytes to %s\n",numbytes3,inet_ntoa(receivepc_addr.sin_addr)); } close(sockfd2); return 0; }