TCP握手交互实例演习

TCP握手交互实例演习

对于TCP握手交互的流程，编写了client跟server来模拟一般的三次握手流程，以及数据交互

首先，编写client跟server，在两个Ubuntu机上进行交互。
接着，用tcpdump或者wireshark进行抓取交流包进行分析

---

1. 编写Server端

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <unistd.h>
#include <pthread.h>
#include <stdlib.h>

void *f(void *arg)
{
    int newsocketfd = (int)arg;
    int size, i = 0;
    while(1)
    {
        char buf[1024];
        bzero(buf, 1024);
        if(-1 == (size = recv(newsocketfd, buf, 1024, 0)))
            perror("recv failed");
        else if(size > 0)
        {
            buf[size] = '\0';
            printf("recv the msg is :%s", buf);
        }else if(size == 0)
        {
            if(i == 2)
                break;
                i++;
        }
    }
    printf("client is exit!\n");
    pthread_exit(NULL);

}

int main(int argc, char **argv)
{
    pthread_t tid = 0;

    int socketfd = socket(AF_INET, SOCK_STREAM, 0);
    if(-1 == socketfd)
        perror("socketfd failed");

    struct sockaddr_in sock_add, client_add;

    if(NULL == memset(&sock_add, 0, sizeof(sock_add)))
        perror("memset failed");
    sock_add.sin_family = AF_INET;
    sock_add.sin_port = htons(0x0979);
    sock_add.sin_addr.s_addr = htonl(INADDR_ANY);
    int sinsize = 1;
    setsockopt(socketfd, SOL_SOCKET, SO_REUSEADDR, &sinsize, sizeof(int));
    if(-1 == bind(socketfd, (struct sockaddr*)(&sock_add),
                 sizeof(struct sockaddr)))
        perror("bind failed");

    if(-1 == listen(socketfd, 8))
        perror("listen failed");

    if(NULL == memset(&client_add, 0, sizeof(client_add)))
        perror("memset failed");

    int size = sizeof(struct sockaddr);
    int newsocketfd;

    newsocketfd = accept(socketfd,
             (struct sockaddr*)(&client_add),&size);
    if(-1 == newsocketfd)
        perror("newsocketfd failed");

    pthread_create(&tid, NULL, f, (void *)newsocketfd);
    while(1)
    {
        char buf[1024];
        fgets(buf, 1024, stdin);    
        if(strcmp(buf, "exit\n") == 0)
            break;
        if(-1 == send(newsocketfd, buf, strlen(buf), 0))
            perror("send failed");
    }

    close(socketfd);
    close(newsocketfd);
    return 0;
}

2. 编写Client端

#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <pthread.h>
#include <unistd.h>

void *f(void *arg)
{
    int socketfd = (int)arg;
    int size, i = 0;
    char buf[1024];
    while(1)
    {
        bzero(buf,1024);
        if(-1 ==(size = recv(socketfd, buf, 1024, 0)))
        {
            perror("recv failed");
        }
        else if(size > 0)
        {
            buf[size] = '\0';
            printf("recv the msg is :%s", buf);
        }else if(size == 0)
        {
            if(i == 2)
                break;
            i++;
        }
    }   
    printf("server is exit!\n");
    pthread_exit(NULL);
}

int main(int argc, char **argv)
{
    if(2 != argc)
    {
        printf("Please input the <%s> <server_addr>\n", argv[0]);
        return -1;
    }

    pthread_t tid = 0;
    int socketfd = socket(AF_INET, SOCK_STREAM, 0);
    if(-1 == socketfd)
        perror("socketfd failed");

    struct sockaddr_in sock_add;

    if(NULL == memset(&sock_add, 0, sizeof(sock_add)))
        perror("memset failed");
    sock_add.sin_family = AF_INET;
    sock_add.sin_port = htons(0x0979);
    inet_pton(AF_INET, argv[1], &sock_add.sin_addr.s_addr);

    int size;
    char buf[1024];
    while(1)
    {
        int newsocketfd = connect(socketfd, 
            (struct sockaddr*)(&sock_add), sizeof(struct sockaddr));
        if(-1 == newsocketfd)
            perror("newsocketfd failed");
        else 
            break;
    }
    pthread_create(&tid, NULL, f, (void *)socketfd);
    while(1)
    {
        bzero(buf,1024);
        fgets(buf, 1024, stdin);
        if(strcmp(buf, "exit\n") == 0)
            break;
        if((-1 ==(size = send(socketfd, buf, 1024, 0))))
        {
            perror("send failed");
        }
    }   
    close(socketfd);

    return 0;
}

3. Client端与Server端交互，并捕获交流包

Client与Server之间交互过程，是通过在PC机上打开了两个Ubuntu的虚拟机，一个当Server，一个当Client，进行交互，同时在PC机上使用Wireshark软件进行捕获网络包。下面是这一过程的详细操作

3.1. 将Server与Client进行编译成可执行档

gcc -o server server.c -lpthread
gcc -o client client.c -lpthread

3.2. 使用Wireshark进行捕获网络包

打开Wireshrak，再选择“本地连接”，再点击“Start”即可捕获PC机上的网络包

3.3. Server与Client在Ubuntu上运行

• 使用两台Ubuntu的虚拟机进行交互模拟，其执行结果如下：
  

4. 分析捕获到的包

• 网络包的分析如下：
  

• 在Wireshark中，选择“统计”–> 流量图，可以出现如下更加清晰的数据交互过程