Protostar/Net 1

If you get stuck, you can watch the solution and explanation here:

Solving network level 1 with socket programming in python.

This level tests the ability to convert binary integers into ascii representation.

This level is at /opt/protostar/bin/net1


#include "../common/common.c"

#define NAME "net1"
#define UID 998
#define GID 998
#define PORT 2998

void run()
  char buf[12];
  char fub[12];
  char *q;

  unsigned int wanted;

  wanted = random();

  sprintf(fub, "%d", wanted);

  if(write(0, &wanted, sizeof(wanted)) != sizeof(wanted)) {
      errx(1, ":(\n");

  if(fgets(buf, sizeof(buf)-1, stdin) == NULL) {
      errx(1, ":(\n");

  q = strchr(buf, '\r'); if(q) *q = 0;
  q = strchr(buf, '\n'); if(q) *q = 0;

  if(strcmp(fub, buf) == 0) {
      printf("you correctly sent the data\n");
  } else {
      printf("you didn't send the data properly\n");

int main(int argc, char **argv, char **envp)
  int fd;
  char *username;

  /* Run the process as a daemon */
  background_process(NAME, UID, GID); 
  /* Wait for socket activity and return */
  fd = serve_forever(PORT);

  /* Set the client socket to STDIN, STDOUT, and STDERR */

  /* Don't do this :> */


See also

Before we continue with the network challenges, let's first introduce the TCP protocol properly. Using netcat and wireshark to understand it.

This is a mirror. Copyright and original can be found here: