Update protocol for #16

doc/protocol.md

@@ -17,17 +17,22 @@ x bytes: [(bytes 8-?): PAYLOAD]
 	- `LIST` (0x00)
 	- `LOAD` (0x01)
 	- `HASH` (0x02)
+	- `DISCOVER` (0x03)
+	- `REGISTER` (0x04)
+	- `UNREGISTER` (0x05)
 
 - RESPONSES (msb is 1):
 	- `LIST` (0x80)
 	- `LOAD` (0x81)
 	- `HASH` (0x82)
+	- `DISCOVER` (0x83)
 	- `VERSION ERROR` (0xC0)
 	- `PROTOCOL ERROR` (0xC1)
 	- `INTERNAL ERROR` (0xC2)
 	- `EMPTY DIRECTORY` (0xC3)
 	- `NOT FOUND` (0xC4)
 	- `EMPTY FILE` (0xC5)
+	- `NOT A TRACKER` (0xC6)
 
 ### List
 Payload size for list request is always zero.
@@ -97,6 +102,47 @@ A algo hash bloc contains:
 
 ```
 
+### Tracker specific messages
+#### Register
+Used by a server to register itself on a tracker.
+Payload contains `0x01` if working on udp, `0x02` if working on tcp, `0x03` if working on both.
+Server may want to do a free `DISCOVER` to check if they have been registered.
+
+#### Unregister
+Used by a server to unregister itself from a tracker.
+Payload contains `0x01` if unregister from udp, `0x02` if unregister from tcp, `0x03` if unregister on both.
+No error is raised if the server was not registered.
+Server may want to do a free `DISCOVER` to check if they have been unregistered.
+
+#### Discover request
+If payload size is null, lists all servers registered.
+If payload contains a filename, list all servers having this file in their list.
+
+```
+? bytes: [<FILENAME>]
+
+```
+
+#### Discover response
+Contains:
+```
+4 bytes: [(bytes  8-11): FILENAME SIZE]
+y bytes: [<FILENAME>]
+? bytes [multiple server blocks] 
+```
+
+Server block is composed with:
+
+```
+2 bytes: [port]
+1 byte: [protocols (udp: 0x01, tcp: 0x02, tcp+udp: 0x03)]
+? bytes: hostname
+\n
+```
+
+#### Not a Tracker
+This error is raised when receiving a DISCOVER, a REGISTER, or an UNREGISTER request,
+but this application is not a tracker.
 
 ### Other response code (errors)
 #### Version error