WPS. Output messaging translation to "human readable"

Question

I'm trying to test the wifi security of my router at home. It has WPS activated. I know WPS should deactivated, I'm only testing...

Reaver is "spitting" a lot of messages, the question is:

What is the meaning of all of that messages?

This is a connection which worked:

[+] Waiting for beacon from XX:XX:XX:...
[+] Associated with XX:XX:XX... (ESSID: WifiTesting)
[+] Trying pin 12345670 
[+] Sending EAPOL START request
[+] Received identity request
[+] Sending identity response
[+] Received M1 message
[+] Sending M2 message
[+] Received M3 message
[+] Sending M4 message
[+] Received M5 message
[+] Sending M6 message
[+] Received M7 message
[+] Sending WSC NACK
[+] Sending WSC NACK
[+] Pin cracked in 6 seconds

Why sometimes it loops over error messages? What they mean?

[!] WPS transaction failed (code: 0x02), re-trying last pin
[!] WPS transaction failed (code: 0x03), re-trying last pin
[!] WPS transaction failed (code: 0x04), re-trying last pin

Answer 1

A very short answer could be:

[+] Waiting for beacon from XX:XX:XX:... -> searching for Access Point
[+] Associated with XX:XX:XX:... (ESSID: WifiTesting) -> Connected by radio
[+] Trying pin 12345670 -> Testing PIN 
[+] Sending EAPOL START request
[+] Received identity request
[+] Sending identity response
[+] Received M1 message -> Router sends its identity / public key
[+] Sending M2 message -> The client sends its identity / public key
[+] Received M3 message
[+] Sending M4 message
[+] Received M5 message -> Confirmed, PIN1 is correct
[+] Sending M6 message
[+] Received M7 message -> Confirmed, PIN2 is correct
[+] Sending WSC NACK -> The client closes communication because it's finished
[+] Sending WSC NACK
[+] Pin cracked in 7 seconds -> The program says the final complete PIN

For the errors:

[!] WPS transaction failed (code: 0x02), re-trying last pin -> no response from AP, timeout
[!] WPS transaction failed (code: 0x03), re-trying last pin -> incorrect packets order, no right answer, usually on M1 or M3
[!] WPS transaction failed (code: 0x04), re-trying last pin -> AP doesn't want to speak with you :)

To understand this, you must know the PIN is divided in two parts (and the checksum of final digit). Please read this interesting info about how WPS works. There explain the three logical components involved in WPS, I extracted an image from there:

This is logical, on common home scenarios like yours, router (registrar role) is usually same device as AP.

Hope this helps