客戶端：int my_read(int fd,void *buf,size_t len);int my_write(int fd,void *buf,size_t len);int pro_echo(int sockfd);int set_fl(int fd,int flags,int on);int main(int argc,char **argv){int sockfd,ret;struct sockaddr_in servaddr;struct hostent *server;char buffer[BUFFER_SIZE];if(argc!=2){fprintf(stderr,"Usage:%s <hostname>\n",argv[0]);return RET_ERR;}server=gethostbyname(argv[1]);if(server==NULL){hstrerror(h_errno);return RET_ERR;}sockfd=socket(AF_INET,SOCK_STREAM,0);if(sockfd<0){perror("socket");return RET_ERR;}ret=set_fl(sockfd,O_NONBLOCK,1);if(ret<0){goto failed;}memset(&servaddr,0,sizeof(servaddr));servaddr.sin_family=AF_INET;servaddr.sin_port=htons(ECHO_PORT);//servaddr.sin_addr.s_addr=*((uint32_t *)(*(server->h_addr_list)));servaddr.sin_addr.s_addr=*(uint32_t *)server->h_addr;ret=connect(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr));if(ret<0){perror("connect");goto failed;}while(1){printf("Enter the message:");if((fgets(buffer,sizeof(buffer)-1,stdin))==NULL){break;}ret=my_write(sockfd,(void *)buffer,strlen(buffer));if(ret<0){perror("write");break;}ret=my_read(sockfd,(void *)buffer,sizeof(buffer)-1);if(ret<0){perror("read");break;}else if(ret==0){printf("server disconnect");break;}buffer[ret]=0;printf("Server echo message:%s\n",buffer);}failed:close(sockfd);return (ret<0 ? RET_ERR : RET_OK);}int my_read(int fd,void *buf,size_t len){int cc,total=0;while(len>0){cc=read(fd,(char *)buf,len);if(cc<0){if(errno==EINTR){continue;}return cc;}if(cc==0){break;}buf=((char *)buf)+cc;total+=cc;len-=cc;}return total;}int my_write(int fd,void *buf,size_t len){int cc,total=0;while(len>0){cc=write(fd,(const char *)buf,len);if(cc<0){if(errno==EINTR);{continue;}return cc;}buf=((char *)buf)+cc;total+=cc;len=len-cc;}return total;}int set_fl(int fd,int flags,int on){int fl;if((fl=fcntl(fd,F_GETFL,0))==-1){perror("fcntl get");return -1;}if(on){fl|=flags;}else{fl&=~flags;}if((fl=fcntl(fd,F_SETFL,fl))==-1){perror("fcntl set");return -1;}return 1;}