TCP三次握手

TCP server

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char *argv[])
{
    int skfd, cnfd, addr_len;
    struct sockaddr_in srv_addr, clt_addr;
    int portnumber=8888;
    char hello[] = "Hello! Long time no see.\n";
    if (2 != argc || 0 > (portnumber = atoi(argv[1])))
    {
        printf("Usage:%s prot\n", argv[0]);
        exit(1);
    } 
    /* 创建IPv4的流式套接字描述符 */
    if (-1 == (skfd = socket(AF_INET, SOCK_STREAM, 0)))
    {
        perror("Socket Error:");
        exit(1);
    }
    /* 填充服务器端sockaddr地址结构 */
    bzero(&srv_addr, sizeof(struct sockaddr_in));
    srv_addr.sin_family = AF_INET;
    srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    srv_addr.sin_port = htons(portnumber);
    /* 将套接字描述符skfd和地址信息结构体绑定起来 */
    if (-1 == bind(skfd, (struct sockaddr *)(&srv_addr), sizeof(struct sockaddr)))
    {
        perror("Bind error");
        exit(1);
    }
    /* 将skfd转换为被动监听模式 */
    if (-1 == listen(skfd, 4))
    {
        perror("Listen error:");
        exit(1);
    }
    while (1)
    {
        /* 调用accept,服务器端一直阻塞，直到客户程序与其建立连接成功为止 */
        addr_len = sizeof(struct sockaddr_in);
        if (-1 == (cnfd = accept(skfd, (struct sockaddr *)(&clt_addr), &addr_len)))
        {
            perror("Accept error:");
            exit(1);
        }
        printf("Connect from %s:%u ...!\n", inet_ntoa(clt_addr.sin_addr), ntohs(clt_addr.sin_port));
        if (-1 == write(cnfd, hello, strlen(hello)))
        {
            perror("Send error");
            exit(1);
        }
        close(cnfd);
    }
    close(skfd);
    exit(0);
}

GDB调试

抓包分析三次握手

• 开启远程抓包,连接tcpServer

./rpcapd -n -d -p10033

nc 192.168.146.129 8888

原文：https://www.cnblogs.com/wangzhilei-src/p/15310092.html