鉴于TCP之简单回传（一） 中所出现的问题，本博文所要采取的一种方法是：
服务器端和客户端共同遵守如下约定： 接收的字节流中，若遇到‘\n‘，表示一次传送完毕。
具体为：
客户端把每次欲发送的数据的最后一个字符设置为 ‘\n‘；
而服务器每次接收时，一个一个字符的从缓冲区中取出一个字符，然后再判断该字符是否为‘\n‘，若不是，则继续读取；若是，则退出循环，表示本次接收结束；
实现代码如下：
//按字符读取--->由于每读取一个字符就产生一次系统调用,故效率较低
ssize_t readline_slow(int fd, void *usrbuf, size_t maxlen)
{
char *bufp = (char*)usrbuf;//偏移位置
ssize_t nread;
size_t nleft = maxlen -1 ;//剩余字节数
char ch;//保存每次读取的字符
while( nleft > 0)//只要还有没读的，就一直循环
{
if(-1 == (nread=read(fd, &ch, 1)))//把从fd中读取的字符存进ch中
{
if(errno == EINTR)//被中断信号打断
continue;
return -1;//err
}else if(0 == nread )
break; //EOF
*bufp = ch;//将读取的字符存进buf
bufp++;//向前移动
nleft --;//剩余字节数--
if(ch == ‘\n‘)//如果该字符为\n。本次读取完成
break;
}
*bufp =‘\0‘;//
return (maxlen- nleft -1);//最大长度 -剩余的字符 - ‘\0‘
}
本程序中所用到的函数都可以在 TCP之函数封装 中找到；
server服务器端：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) do { perror(m); exit(EXIT_FAILURE); }while(0)
void do_server(int fd);
int main(int argc, const char *argv[])
{
//socket
int listenfd = socket(AF_INET, SOCK_STREAM, 0 );
if( -1 == listenfd)
ERR_EXIT("socket");
//地址复用
int on = 1;
if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof on) < 0)
ERR_EXIT("setsockopt");
//bind
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(8888); //主机字节序转化为网络字节序
addr.sin_addr.s_addr = inet_addr("127.0.0.1");//点分十进制转化成网络字节序
if( -1 == bind( listenfd, (struct sockaddr*)&addr, sizeof(addr)))
ERR_EXIT("bind");
//listen
if( -1 == listen(listenfd,SOMAXCONN ))
ERR_EXIT("listen");
//accept
int peerfd = accept(listenfd, NULL, NULL);//对方的IP&PORT
//read&write
do_server(peerfd);
//close
close(peerfd);
close(listenfd);
return 0;
}
void do_server(int fd)
{
char recvbuf[1024100] = {0};
int cnt =0;
while(1)
{
int nread = readline_slow(fd, recvbuf, sizeof(recvbuf));
if(nread == -1)//err
{
if(errno == EINTR)
continue;
ERR_EXIT("read");
}else if (nread == 0 )//write close
{
printf("close...\n");
exit(EXIT_FAILURE);
}
// ok
printf("count = %d recv size = %d\n",++cnt, nread);
memset(recvbuf, 0, sizeof(recvbuf));
}
}
client客户端：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) do { perror(m); exit(EXIT_FAILURE); }while(0)
void do_server(int fd);
int main(int argc, const char *argv[])
{
//socket
int peerfd = socket(AF_INET, SOCK_STREAM,0);
if( -1 == peerfd)
ERR_EXIT("socket");
//connect
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_port = htons(8888);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
if( -1 == connect(peerfd,(struct sockaddr*)&addr, sizeof(addr) ))
ERR_EXIT("connect");
//read&write
do_server(peerfd);
return 0;
}
void do_server(int fd)
{
#define SIZE 1024
char sendbuf[SIZE +1]= {0};
int i ;
for (i = 0; i < SIZE-1; i++) //attention
{
sendbuf[i]= ‘a‘;
}
sendbuf[SIZE-1] = ‘\n‘;//标志位
int cnt =0;
while(1)
{
int i;
for (i = 0; i < 10; i++)
{
int nwrite =writen(fd, sendbuf, SIZE);//发送SIZE个数据中最后一个字符为\n
if( nwrite != SIZE)
ERR_EXIT("writen");
printf("cout = %d,write %d bytes\n",++cnt, SIZE);
}
nano_sleep(4.5);
}
}
测试结果：
./server count = 1 recv size = 1024 count = 2 recv size = 1024 count = 3 recv size = 1024 count = 4 recv size = 1024 count = 5 recv size = 1024 count = 6 recv size = 1024 count = 7 recv size = 1024 count = 8 recv size = 1024 count = 9 recv size = 1024 count = 10 recv size = 1024 count = 11 recv size = 1024 count = 12 recv size = 1024 count = 13 recv size = 1024 count = 14 recv size = 1024 count = 15 recv size = 1024 count = 16 recv size = 1024 count = 17 recv size = 1024 count = 18 recv size = 1024 count = 19 recv size = 1024 count = 20 recv size = 1024
./client count = 1 recv size = 1024 count = 2 recv size = 1024 count = 3 recv size = 1024 count = 4 recv size = 1024 count = 5 recv size = 1024 count = 6 recv size = 1024 count = 7 recv size = 1024 count = 8 recv size = 1024 count = 9 recv size = 1024 count = 10 recv size = 1024 count = 11 recv size = 1024 count = 12 recv size = 1024 count = 13 recv size = 1024 count = 14 recv size = 1024 count = 15 recv size = 1024 count = 16 recv size = 1024 count = 17 recv size = 1024 count = 18 recv size = 1024 count = 19 recv size = 1024 count = 20 recv size = 1024
注意：本程序效率比较低下，原因在于：
每次读取一个字符都要系统调用一次read函数。
解决方法：TCP之简单回传（四）
时间： 2024-10-12 20:10:33