text: #include "tcp.h"
  #include <iostream>
  using namespace std;
  
  int main()
  {
      tcp_connection conn("127.0.0.1", 8000);
      char msg[] = "hello, world";
      conn.writen(msg, sizeof(msg));
      char res[BUFSIZ];
      conn.read(res, BUFSIZ);
      cout << "res: " << res << endl;
  }
  