Linux网络编程之TCP粘包问题3

1.解决TCP粘包问题的另一种解决方案是在应用层实现数据包之间的分离。
比如下面的例子，以 字符 “\n”作为两个数据包之间的分隔符。
note: client端并没有实现用“\n”分割收到的数据
TCP server：

/*description:
  1. tcp server: seprate the received data using "\n"
  2. send the received data back to client */
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include<errno.h>

ssize_t readn(int fd, void *buf, size_t count)
{
    int n_left = count;
    int n_read;
    char * readbuf = (char *)buf;
    while (n_left > 0)
    {
        if ((n_read = read(fd, readbuf, n_left)) < 0)
        {
            if (errno == EINTR)
                continue;
            return -1;
        }
        else if (n_read == 0)
        {
            printf ("client has closed\n");
            break;
        }
        printf ("1. receive data is %s, length is %d,lef data:%d\n", readbuf, n_read, n_left - n_read);
        readbuf += n_read;
        n_left -= n_read;
        printf("left data is %d\n", n_left);
    }
    return count - n_left;
}
ssize_t writen(int fd, const void *buf, size_t count)
{
    int n_left = count;
    int n_written;
    char * writebuf = (char *)buf;
    while (n_left > 0)
    {
        if ((n_written = write(fd, writebuf, n_left)) < 0)
        {
            if (errno == EINTR)
                continue;
            return -1;
        }
        else if (n_written == 0)
        {
            continue;
        }
        writebuf += n_written;
        n_left -= n_written;
    }
    return count - n_left;
}
ssize_t readline(int fd, void *buf, size_t count)
{
    int n_left = count;
    int n_read = 0;
    int ret = 0;
    int loop_index;
    char *readbuf = (char *) buf;
    while (1)
    {
        if ((n_read = recv(fd, buf, n_left, MSG_PEEK)) < 0)
        {
            perror("read error\n");
            exit(-1);
        }
        else if (n_read == 0)
        {
            printf("client closed connection\n");
            exit(1);
        }
        for (loop_index=0; loop_index < n_read; loop_index++)
        {
            if (readbuf[loop_index] == '\n')
            {
                printf("get \n from buffer\n");
                n_read = readn(fd, buf, loop_index + 1);
                if (n_read != loop_index + 1)
                {
                    perror("read error");
                    exit(-1);
                }
                return n_read;
            }
        }
        if (n_read > n_left)
            exit(EXIT_FAILURE);
        ret = readn(fd, buf, n_read);
        if(ret != n_read)
        {
            perror("read error");
            exit(-1);
        }
        n_left -= n_read;
        buf += n_read;
    }
    return -1;
}
int main()
{
    int listenfd = 0;
    if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket error\n");
        exit(1);
    }
    printf("creat socket success\n");
    struct sockaddr_in seraddr;
    memset(&seraddr, 0, sizeof(seraddr));
    seraddr.sin_family = AF_INET;
    seraddr.sin_port = htons(51888);
    seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    if (bind(listenfd, (struct sockaddr *)&seraddr,sizeof(seraddr)) < 0)
    {
        perror("bind error\n");
        exit(1);
    }
    printf("bind success\n");
    if (listen(listenfd, 50) < 0)    
    {
        perror("listen error\n");
        exit(1);
    }
    printf("listen success\n");
    struct sockaddr_in peer_addr;
    socklen_t addr_len = sizeof(peer_addr);
    memset(&peer_addr, 0, sizeof(peer_addr));
    int conid;
    if ((conid = accept(listenfd, (struct sockaddr *)&peer_addr, &addr_len)) < 0) 
    {
        perror("listen error\n");
        exit(1);
    }
    printf("accept success\n");
    printf("peer address is %s, port is %d\n", inet_ntoa(peer_addr.sin_addr),ntohs(peer_addr.sin_port));
    char recbuf[50];
    while (1)
    {
        memset(recbuf, 0, sizeof(recbuf));
        printf("start one new readline\n");
        int ret = readline(conid, recbuf, sizeof(recbuf));
        if (ret == 0)
        {
            break;
        }
        printf ("receive data is %s, length is %d\n", recbuf, ret);
        writen(conid, recbuf, ret);
        printf ("send data is %s to client,length is %d\n", recbuf, ret);
    }
    close(listenfd);
    close(conid);
    
    return 0;
}

TCP client:

#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
ssize_t readn(int fd, void *buf, size_t count)
{
    int n_left = count;
    int n_read;
    char * readbuf = (char *)buf;
    while (n_left > 0)
    {
        if ((n_read = read(fd, readbuf, n_left)) < 0)
        {
            if (errno == EINTR)
                continue;
            return -1;
        }
        else if (n_read == 0)
        {
            printf ("client has closed\n");
            break;
        }
        printf ("1. receive data is %s, length is %d,lef data:%d\n", readbuf, n_read, n_left - n_read);
        readbuf += n_read;
        n_left -= n_read;
        printf("left data is %d", n_left);
    }
    return count - n_left;
}
ssize_t writen(int fd, const void *buf, size_t count)
{
    int n_left = count;
    int n_written;
    char * writebuf = (char *)buf;
    while (n_left > 0)
    {
        if ((n_written = write(fd, writebuf, n_left)) < 0)
        {
            if (errno == EINTR)
                continue;
            return -1;
        }
        else if (n_written == 0)
        {
            continue;
        }
        writebuf += n_written;
        n_left -= n_written;
    }
    return count - n_left;
}

int main()
{
    int confd = 0;
    if((confd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket error\n");
        exit(1);
    }
    printf("create socket success\n");
    struct sockaddr_in seraddr;
    memset(&seraddr, 0, sizeof(seraddr));
    seraddr.sin_family = AF_INET;
    seraddr.sin_port = htons(51888);
    seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    if (connect(confd, (struct sockaddr *)&seraddr, sizeof(seraddr)) < 0)
    {
        perror("connect error\n");
        exit(1);
    }
    printf ("connect to server success\n");
    char sendbuf[50] = {0};
    char recbuf[50] = {0};
    while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
    {
        writen(confd, sendbuf, strlen(sendbuf));
        read(confd, recbuf, sizeof(recbuf));
        printf ("receive data:%s\n", recbuf);
        memset(sendbuf, 0, sizeof(sendbuf));
        memset(recbuf, 0, sizeof(recbuf));
    }
    close(confd); 

    return 0;
}