linux下自定义协议防止粘包问题

目的：防止服务器与客户端常见的粘包问题
思路：自定义结构体，把发送数据帧的长度与数据帧进行分装，以防止客户端与服务器之间的粘包问题

服务器端代码：

/*************************************************************************
    > File Name: test.c
    > Author: kinght
    > Mail: zhjnight@163.com 
    > Created Time: Wed 20 Jun 2018 06:58:02 PM PDT
 ************************************************************************/

#include<stdio.h>
#include <sys/socket.h>   //connect,send,recv,setsockopt等
#include <sys/types.h>      

#include <netinet/in.h>     // sockaddr_in, "man 7 ip" ,htons
#include <poll.h>             //poll,pollfd
#include <arpa/inet.h>   //inet_addr,inet_aton
#include <unistd.h>        //read,write
#include <netdb.h>         //gethostbyname

#include <error.h>         //perror
#include <stdio.h>
#include <errno.h>         //errno

#include <string.h>          // memset
#include <string>
#include <iostream>
#include<stdlib.h>
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

#define ERR_EXIT(m)\
    do\
{\
    perror(m);\
    exit(EXIT_FAILURE);\
}while(0)

struct packet
{
   int len;
   char buf[1024];
};

ssize_t readn(int fd,void *buf,size_t count)
{
//printf("%d\n",count);

        size_t nleft = count;
        ssize_t nread;
        char *bufp = (char*)buf;
//fputs(bufp,stdout);
        while(nleft>0)
        {
            nread = read(fd,bufp,nleft);
//printf("%d\n",nread);
//fputs(bufp,stdout);
            if(nread <0)
            {
              if(errno = EINTR)
              {
                return -1;
              }
            }
            else if(nread == 0)
            {
               break;
            }
            else
            {
            bufp += nread;
            nleft -= nread;
            }

        }
}

ssize_t written(int fd,void *buf,size_t count)
{
//printf("%d",count);

        size_t nleft = count;
        ssize_t nwritten;
        char *bufp = (char*)buf;
//fputs(bufp,stdout);
        while(nleft>0)
        {
            nwritten = write(fd,bufp,nleft);
            if(nwritten <0)
            {
              if(errno = EINTR)
              {
                return -1;
              }
            }
            else if(nwritten == 0)
            {
               continue;
            }
           else
           {
            bufp += nwritten;
            nleft= nleft -nwritten;
            //printf("%d",nleft);
            }


        }
}

void doServiceConn(int conn)
{
          /*char recvbuf[1024];
      while(true)
      {
       memset(recvbuf,0,sizeof(recvbuf));
       int ret = readn(conn,recvbuf,4);
       if(ret == 0)
       {
           printf("client close");
           break;
       }
       else if(ret == -1)
       {
           ERR_EXIT("read");
       }

       written(conn,recvbuf,sizeof(recvbuf));
       printf(recvbuf,stdout);
      }*/   
 struct packet  recvbuf;
 memset(&recvbuf,0,sizeof(recvbuf));
 int n;
 while(true)
 {
  int ret = readn(conn,&recvbuf.len,4);
  if(ret == -1)
     ERR_EXIT("read");
  else if(ret < 4)
  {
   printf("peer close");
   break;
  }
  n= ntohl(recvbuf.len);
  ret = readn(conn,recvbuf.buf,n);
  if(ret == -1)
  {
   ERR_EXIT("read");
  }
  else if(ret < n)
  {
  printf("client close");
  break;
  }
  fputs(recvbuf.buf,stdout);
  written(conn,&recvbuf,4+n);

 } 

}
int main(void)
{
    int listenfd;
    if((listenfd =socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<0)
    {
        ERR_EXIT("ERROR");
    }
    struct sockaddr_in servaddr;
    memset(&servaddr,0,sizeof(servaddr));
    servaddr.sin_family=AF_INET;
    servaddr.sin_port = htons(5188);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    int on = 1;
    if(setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on))< 0)
    {
    ERR_EXIT("SETSOCKOPT");
    }
    if(bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr))< 0)
    {
        ERR_EXIT("error");
    }
    if(listen(listenfd,SOMAXCONN)<0)
    {
        ERR_EXIT("listen");
    }
    struct sockaddr_in peeraddr;
    socklen_t peerlen = sizeof(peeraddr);
    int conn;
        pid_t pid;
        while(1)
        {
          conn = accept(listenfd,(struct sockaddr*)&peeraddr,&peerlen);
      if(conn < 0)
      {
       ERR_EXIT("accept");
      }
      printf("ip= %s,port = %d\n",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));
          pid = fork();
          if(pid == -1)
              ERR_EXIT("fork");
          if(pid == 0)
          {
             close(listenfd);
             doServiceConn(conn);
         exit(EXIT_SUCCESS);
          }
          else
          {
             close(conn);
          }
        }

    return 0;
}

客户端代码：

/*************************************************************************
    > File Name: client.c
    > Author: kinght
    > Mail: zhjnight@163.com 
    > Created Time: Wed 20 Jun 2018 06:58:02 PM PDT
 ************************************************************************/

#include<stdio.h>
#include <sys/socket.h>   //connect,send,recv,setsockopt等
#include <sys/types.h>      

#include <netinet/in.h>     // sockaddr_in, "man 7 ip" ,htons
#include <poll.h>             //poll,pollfd
#include <arpa/inet.h>   //inet_addr,inet_aton
#include <unistd.h>        //read,write
#include <netdb.h>         //gethostbyname

#include <error.h>         //perror
#include <stdio.h>
#include <errno.h>         //errno

#include <string.h>          // memset
#include <string>
#include <iostream>
#include<stdlib.h>
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

#define ERR_EXIT(m)\
    do\
{\
    perror(m);\
    exit(EXIT_FAILURE);\
}while(0)

struct packet
{
   int len;
   char buf[1024];
};

ssize_t readn(int fd,void *buf,size_t count)
{
        size_t nleft = count;
        ssize_t nread;
        char *bufp = (char*)buf;
        while(nleft>0)
        {
            nread = read(fd,bufp,nleft);
            if(nread <0)
            {
              if(errno = EINTR)
              {
                return -1;
              }
            }
            else if(nread == 0)
            {
               break;
            }
            else
            {
            bufp += nread;
            nleft -= nread;
            }

        }
}

ssize_t written(int fd,void *buf,size_t count)
{
//printf("%d",count);

        size_t nleft = count;
        ssize_t nwritten;
        char *bufp = (char*)buf;
//fputs(bufp,stdout);
        while(nleft>0)
        {
            nwritten = write(fd,bufp,nleft);
            if(nwritten <0)
            {
              if(errno = EINTR)
              {
                return -1;
              }
            }
            else if(nwritten == 0)
            {
               continue;
            }
           else
           {
            bufp += nwritten;
            nleft= nleft -nwritten;
            //printf("%d",nleft);
            }


        }
}


int main(void)
{
    int sock;
    if((sock =socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<0)
    {
        ERR_EXIT("ERROR");   
    }
    struct sockaddr_in servaddr;
    memset(&servaddr,0,sizeof(servaddr));
    servaddr.sin_family=AF_INET;
    servaddr.sin_port = htons(5188);
    servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    if(connect(sock,(struct sockaddr*)&servaddr,sizeof(servaddr))< 0)
    {
    ERR_EXIT("connect");
    }
    //char sendbuf[1024]={0};
    //char recvbuf[1024]={0};
        struct packet sendbuf;
        struct packet recvbuf;
        memset(&sendbuf,0,sizeof(sendbuf));
        memset(&recvbuf,0,sizeof(recvbuf));
        int n;
    while(fgets(sendbuf.buf,sizeof(sendbuf.buf),stdin)!=NULL)
    {
    /*written(sock,sendbuf,strlen(sendbuf));
    readn(sock,recvbuf,sizeof(recvbuf));
    fputs(recvbuf,stdout);
    memset(sendbuf,0,sizeof(sendbuf));
    memset(recvbuf,0,sizeof(recvbuf));*/
                        n = strlen(sendbuf.buf);
                        sendbuf.len = htonl(n);
                        written(sock,&sendbuf,4+n);
                   int ret = readn(sock,&recvbuf.len,4);
            if(ret == -1)
                ERR_EXIT("read");
            else if(ret < 4)
            {
                printf("peer close");
                                break;
            }
                        n = ntohl(recvbuf.len);
                        ret = readn(sock,recvbuf.buf,n);
                        if(ret == -1)
                        {
                         ERR_EXIT("read");
                        }
                        else if (ret < n)
                        {
                         printf("client close\n");
                         break;
                        }
                       fputs(recvbuf.buf,stdout);
                  memset(&sendbuf,0,sizeof(sendbuf));
                      memset(&recvbuf,0,sizeof(recvbuf));
    }
    close(sock);
    return 0;
}