tcp/ip通信第5期之客户机端程序

 /*此程序是tcp/ip通信的客户机端程序，
   测试运行在redhat6系统上
   重构readline函数，解决粘包问题——利用“\n”识别一个消息边界
 */
 #include<stdio.h>
 #include<stdlib.h>
 #include<unistd.h>
 #include<sys/types.h>
 #include<sys/socket.h>
 #include<arpa/inet.h>
 #include<netinet/in.h>
 #include<string.h>
 #include<signal.h>
 #include<errno.h>

 #define port 5188

 ssize_t readn(int fd, void *buf, size_t count)
 {
     size_t nleft = count;//还留下多少字节没有读
     ssize_t nread; //已经读了多少字节
     char *bufp = (char *)buf;
     while (nleft > )
             {
                 if ((nread = read(fd, bufp, nleft)) < )
                 {
                     if (errno == EINTR)
  //被信号中断，errno这个全局变量的值就会等于EINTR。
                         continue;
                     return -;
                 }
                 else if (nread == ) //对方关闭或者已经读到eof
                     return count - nleft;
                 bufp += nread;
                 nleft -= nread;
             }
             return count;
 }

 ssize_t writen(int fd, const void * buf, size_t count)
 {
         size_t nleft = count;
         ssize_t nwritten;
         char *bufp = (char *)buf;
         while (nleft > )
             {
                 if ((nwritten = write(fd, bufp, nleft)) < )
                 {
                     if (errno == EINTR)
                         continue;
  //要保证读取的字节数为指定字节数，所以继续
                     return -;
                 }
                 else if (nwritten == )
                     continue;
  //由于其他原因引起的什么都没有写进，则继续操作，保证指定字节数
                 bufp += nwritten;
                 nleft -= nwritten;
             }
             return count;
 }

 ssize_t recv_peek(int sockfd,void *buf,size_t len)
 {
     while()
     {
         int ret=recv(sockfd,buf,len,MSG_PEEK);
         if(ret==-&&errno==EINTR)
             continue;
         return ret;
     }
 }

 ssize_t recv_line(int sockfd,void *buf,size_t len)
 {
     int ret;//记录函数返回值
     int nread;//已经读到的字节数
     char *bufp=buf;
     int nleft=len;
     while()
     {
         ret=recv_peek(sockfd,bufp,nleft);
         if(ret<)
             return ret;
         else if(ret==)
             return ret;
         nread=ret;
         int i;
         for(i=;i<nread;i++)
         {
             if(bufp[i]=='\n')
             {
                 ret=readn(sockfd,bufp,i+);
                 if(ret!=i+)
                     exit();
                 return ret;
             }
         }
         if(nread>nleft)
             exit();
         nleft -= nread;
         ret=readn(sockfd,bufp,nread);
         if(ret!=nread)
             exit();
         bufp+=nread;
     }
     return -;
 }

 int main()
 {
     int sock;
     //*****创建套接字*******
     if((sock=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<)
     /*if((listenfd=socket(PF_INET,SOCK_STREAM,0))<0)*/
         perror("error");

     //*******ipv4地址结构**********
     struct sockaddr_in servaddr;
     memset(&servaddr,,sizeof(servaddr)); //清空结构体变量
     servaddr.sin_family=AF_INET;
     servaddr.sin_port= htons(port); //使用端口号：5188
     servaddr.sin_addr.s_addr=inet_addr("192.168.248.129");  //ip地址使用对方的地址，即服务器地址
     printf("the port_id:%d\n",port);

     //*********连接请求************
     if(connect(sock,(struct sockaddr*)(&servaddr),sizeof(servaddr))<)  //使用对方的ip地址
         perror("error");
     else
         printf("connected success.\n");

     //************通信过程*************
     char sendbuf[]={};
     char recvbuf[]={};
     while(fgets(sendbuf,sizeof(sendbuf),stdin)!=NULL)
     {
         writen(sock,sendbuf,strlen(sendbuf));
         int ret=recv_line(sock,recvbuf,sizeof(recvbuf));
         if(ret==-)
             perror("error\n");
         if(ret==)
         {
             printf("peer is closed.\n");
             break;
         }

         fputs(recvbuf,stdout);
         memset(sendbuf,,sizeof(sendbuf)); //清空缓存
         memset(recvbuf,,sizeof(recvbuf));
     }
     close(sock);
     return ;
 }