Break into the following service that runs on port 54321:
(Backup copy of binary available here)

Source code sample:
void handle(void){
  var v4 = 0;
  char buf[0x200];
  memset(&buf, 0, 0x200u);
  send(fd, "Wecome to my first CS project.\nPlease type your name:  ", 0x37u, 0);
  recv(fd, &buf, 0x204u, 0);
  v3 = 0;
  if ( !strcmp(&buf, "(SOME UNKNOWN STRING)") )
    v4 = 1;
  if ( v4 )
  {
    ::fd = (int)fopen("./key", "r");
    __isoc99_fscanf(::fd, "%s", &buf);
    recv(fd, 0, 0x10u, 64);
    send(fd, &buf, 0x200u, 0);
  }
}