#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <string.h>#include <unistd.h>#include <netdb.h>#include <sys/socket.h>#include <netinet/in.h>#include <sys/types.h>#include <arpa/inet.h>#define SERVER_PORT 8888 #define MAX_BUF_SIZE 1024 void udpc_requ(int sockfd,const struct sockaddr_in *addr,int len) {     char buffer[MAX_BUF_SIZE];     int n;     while(1)     {     /* 从键盘读入,写到服务端 */         printf("Please input char:\n");        fgets(buffer,MAX_BUF_SIZE,stdin);         sendto(sockfd,buffer,strlen(buffer),0,(struct sockaddr *)addr,len);         bzero(buffer,MAX_BUF_SIZE);     } } int main(int argc,char **argv) {     int sockfd;     struct sockaddr_in addr;     if(argc!=2)     {         fprintf(stderr,"Usage:%s server_ip\n",argv[0]);         exit(1);     }    /* 建立 sockfd描述符 */     sockfd=socket(AF_INET,SOCK_DGRAM,0);     if(sockfd<0)     {         fprintf(stderr,"Socket Error:%s\n",strerror(errno));         exit(1);     }     /* 填充服务端的资料 */     bzero(&addr,sizeof(struct sockaddr_in));     addr.sin_family=AF_INET;     addr.sin_port=htons(SERVER_PORT);    if(inet_aton(argv[1],&addr.sin_addr)<0)  /*inet_aton函数用于把字符串型的IP地址转化成网络2进制数字*/     {         fprintf(stderr,"Ip error:%s\n",strerror(errno));         exit(1);     }     udpc_requ(sockfd,&addr,sizeof(struct sockaddr_in)); // 进行读写操作    close(sockfd); } #include <stdlib.h>#include <stdio.h>#include <errno.h>#include <string.h>#include <unistd.h>#include <netdb.h>#include <sys/socket.h>#include <netinet/in.h>#include <sys/types.h>#include <arpa/inet.h>#define SERVER_PORT 8888 #define MAX_MSG_SIZE 1024 void udps_respon(int sockfd) {     struct sockaddr_in addr;     int addrlen,n;     char msg[MAX_MSG_SIZE];     while(1)     {    /* 从网络上读,并写到网络上 */         bzero(msg,sizeof(msg)); // 初始化,清零        addrlen = sizeof(struct sockaddr);        n=recvfrom(sockfd,msg,MAX_MSG_SIZE,0,(struct sockaddr*)&addr,&addrlen); // 从客户端接收消息        msg[n]=0;//将收到的字符串尾端添加上字符串结束标志         /* 显示服务端已经收到了信息 */         fprintf(stdout,"Server have received %s",msg); // 显示消息    } } int main(void) {     int sockfd;     struct sockaddr_in addr;     /* 服务器端开始建立socket描述符 */     sockfd=socket(AF_INET,SOCK_DGRAM,0);     if(sockfd<0)     {         fprintf(stderr,"Socket Error:%s\n",strerror(errno));         exit(1);     }     /* 服务器端填充 sockaddr结构 */     bzero(&addr,sizeof(struct sockaddr_in));     addr.sin_family=AF_INET;     addr.sin_addr.s_addr=htonl(INADDR_ANY);     addr.sin_port=htons(SERVER_PORT);     /* 捆绑sockfd描述符 */     if(bind(sockfd,(struct sockaddr *)&addr,sizeof(struct sockaddr_in))<0)     {         fprintf(stderr,"Bind Error:%s\n",strerror(errno));         exit(1);     }     udps_respon(sockfd); // 进行读写操作    close(sockfd); }