udp client 常式

#include<stdlib.h>#include<stdio.h>#include<string.h>#include<sys/types.h>#include<sys/socket.h>#include<netinet/in.h>#include<netdb.h>void print_usage(char* str){printf("the command %s usage is:\n",str);printf("%s Ip_Address [port] \n");}int main(int argc,char**argv){int sockfd;struct sockaddr_in server;struct sockaddr_in reply;char send_buf[2048];char recv_buf[2048];int length;int sendnum;int recvnum;int port;port =atoi(argv[2]);if ((2>argc) ||(argc>3)){print_usage(argv[0]);exit(1);}/*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 DEBUGprintf("the sokcet id is %d\n",sockfd);printf("enter data exchange  phrase....\n");#endif/*1.2 setting the destinate address */memset(&server,0,sizeof(struct sockaddr));server.sin_family = AF_INET;server.sin_addr.s_addr = inet_addr(argv[1]);server.sin_port = htons(port);/* The Second Stage: data exchange phrase */memset(&send_buf,0,sizeof(send_buf));memset(&recv_buf,0,sizeof(recv_buf));printf("what words do you want to tell to server:\n");gets(send_buf);          /* send  the data to the server*/sendnum = strlen(send_buf);if(0>sendto(sockfd,send_buf,sendnum,0,(struct sockaddr*)&server,sizeof(struct sockaddr))){perror("send data error\n");close(sockfd);exit(0);}recvnum = recvfrom(sockfd,recv_buf,sizeof(recv_buf),0,(struct sockaddr *)&server,&length);if (0>recvnum){perror("receive data error\n");close(sockfd);exit(0);}recv_buf[recvnum]='\0';printf("the message from the server is :%s\n",recv_buf);close(sockfd);exit(0);}