# P2P-JAVA-PROJECT version 1 (Protocol for step 1)
All messages begins with `P2P-JAVA-PROJECT VERSION 1.0\n` (this version of the protocol).

## Client messages
- `LIST\n`: ask the server to list files from server root directory
- `DOWNLOAD\n<FILENAME>\n`: ask the server to download file <FILENAME> from server root directory. Only one filename is allowed per request.

## Server responses
- The response to `LIST` request is in the format `LIST\n<FILENAME 1>\n<FILENAME 2>\n[…]<LAST FILENAME>\n\n`
- The response to `DOWNLOAD` request is `LOAD\n<FILESIZE (BYTES)>\n<POSITION>\n<CONTENT OF FILE>` or `NOT FOUND\n` if the file doesn't exists.
- The server send a `PROTOCOL ERROR\n` message if it doesn't understands what the client sent.
- The server send a `INTERNAL ERROR\n` message if it encounters an internal error.

# P2P-JAVA-PROJECT version 1.1 (Binary protocol for step 1)

All strings in the datagram are utf-8 encoded.

```Datagram format

1 byte:  [0-7: VERSION(0x11, first quartet is major version, second is minor)]
1 byte:  [8-15: REQUEST/RESPONSE CODE]
2 bytes: [16-31: RESERVED FOR FUTURE USE]
4 bytes: [32-63: PAYLOAD SIZE IN BYTES]
x bytes: [64-xx: PAYLOAD]

```

## Requests and responses codes
- REQUESTS (msb is 0):
	- `LIST` (0x00)
	- `LOAD` (0x01)

- RESPONSES (msb is 1):
	- `LIST` (0x80)
	- `LOAD` (0x81)
	- `VERSION ERROR` (0xC0)
	- `PROTOCOL ERROR` (0xC1)
	- `INTERNAL ERROR` (0xC2)
	- `EMPTY DIRECTORY` (0xC3)
	- `NOT FOUND` (0xC4)
	- `EMPTY FILE` (0xC5)

### List
Payload size for list request is always zero.
Payload for list response is filenames separated by `\n`. Payload size for list response is never zero.

#### Empty directory
When directory is empty.
Payload size for empty directory is always zero.


### Load
#### Not found
Response when the file requested is not found on the server.
Payload size for Not found is zero.


#### Load response
Payload contains

```
8 bytes: [64-127: OFFSET OF FILE CONTENT IN BYTES]
8 bytes: [128-191: TOTAL FILESIZE]
4 bytes: [192-223: FILENAME SIZE] (cannot be > to PAYLOAD_SIZE - 20 or be zero)
y bytes: [<FILENAME>]
z bytes: [FILE CONTENT]
```

#### Load request
Payload contains only the name of the file to load.

### Other response code (errors)
#### Version error
Response when datagram received use wrong version code.

#### Protocol error
Response when the request cannot be interpreted (but version is correct).
Payload size for Protocol error is zero

#### Internal error
Response in internal failure case.
Payload size for Internal error is zero.