This is a bug test for reproducing tcp syn+ack retransmission bug, this is not going to work good

BadListener.c

#include <netinet/in.h>    // for sockaddr_in
#include <sys/types.h>    // for socket
#include <sys/socket.h>    // for socket
#include <stdio.h>        // for printf
#include <stdlib.h>        // for exit
#include <string.h>        // for bzero
/*
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
*/
#define HELLO_WORLD_SERVER_PORT    7777 
#define LENGTH_OF_LISTEN_QUEUE 1
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512
 
int main(int argc, char **argv)
{
    //设置一个socket地址结构server_addr,代表服务器internet地址, 端口
    struct sockaddr_in server_addr;
    bzero(&server_addr,sizeof(server_addr)); //把一段内存区的内容全部设置为0
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htons(INADDR_ANY);
    server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);
 
    //创建用于internet的流协议(TCP)socket,用server_socket代表服务器socket
    int server_socket = socket(PF_INET,SOCK_STREAM,0);
    if( server_socket < 0)
    {
        printf("Create Socket Failed!");
        exit(1);
    }
{ 
   int opt =1;
   setsockopt(server_socket,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
}
     
    //把socket和socket地址结构联系起来
    if( bind(server_socket,(struct sockaddr*)&server_addr,sizeof(server_addr)))
    {
        printf("Server Bind Port : %d Failed!", HELLO_WORLD_SERVER_PORT); 
        exit(1);
    }
 
    //server_socket用于监听
    if ( listen(server_socket, LENGTH_OF_LISTEN_QUEUE) )
    {
        printf("Server Listen Failed!"); 
        exit(1);
    }
    while (1) //服务器端要一直运行
    {
        //do nothing
    }
    //关闭监听用的socket
    close(server_socket);
    return 0;
    }

Compile this code on a linux and telnet to port 7777, send something, and use ctrl+] to quit the telnet session, repeat again for one or two times, you will see syn+ack and ack retransmission on wireshark