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# P2P-JAVA-PROJECT version 1 (Protocol for step 1)
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All messages begins with `P2P-JAVA-PROJECT VERSION 1.0\n` (this version of the protocol).
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## Client messages
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- `LIST\n`: ask the server to list files from server root directory
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- `DOWNLOAD\n<FILENAME>\n`: ask the server to download file <FILENAME> from server root directory. Only one filename is allowed per request.
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## Server responses
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- The response to `LIST` request is in the format `LIST\n<FILENAME 1>\n<FILENAME 2>\n[…]<LAST FILENAME>\n\n`
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- 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.
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- The server send a `PROTOCOL ERROR\n` message if it doesn't understands what the client sent.
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- The server send a `INTERNAL ERROR\n` message if it encounters an internal error.
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# P2P-JAVA-PROJECT version 1.1 (Binary protocol for step 1)
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All strings in the datagram are utf-8 encoded.
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```Datagram format
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1 byte: [0-7: VERSION(0x11, first quartet is major version, second is minor)]
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1 byte: [8-15: REQUEST/RESPONSE CODE]
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2 bytes: [16-31: RESERVED FOR FUTURE USE]
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4 bytes: [32-63: PAYLOAD SIZE IN BYTES]
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x bytes: [64-xx: PAYLOAD]
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```
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## Requests and responses codes
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- REQUESTS (msb is 0):
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- `LIST` (0x00)
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- `LOAD` (0x01)
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- RESPONSES (msb is 1):
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- `LIST` (0x80)
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- `LOAD` (0x81)
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- `VERSION ERROR` (0xC0)
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- `PROTOCOL ERROR` (0xC1)
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- `INTERNAL ERROR` (0xC2)
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- `EMPTY DIRECTORY` (0xC3)
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- `NOT FOUND` (0xC4)
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- `EMPTY FILE` (0xC5)
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### List
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Payload size for list request is always zero.
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Payload for list response is filenames separated by `\n`. Payload size for list response is never zero.
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#### Empty directory
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When directory is empty.
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Payload size for empty directory is always zero.
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### Load
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#### Not found
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Response when the file requested is not found on the server.
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Payload size for Not found is zero.
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#### Load response
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Payload contains
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```
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8 bytes: [64-127: OFFSET OF FILE CONTENT IN BYTES]
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8 bytes: [128-191: TOTAL FILESIZE]
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4 bytes: [192-223: FILENAME SIZE] (cannot be > to PAYLOAD_SIZE - 20 or be zero)
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y bytes: [<FILENAME>]
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z bytes: [FILE CONTENT]
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```
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#### Load request
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Payload contains only the name of the file to load.
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### Other response code (errors)
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#### Version error
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Response when datagram received use wrong version code.
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#### Protocol error
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Response when the request cannot be interpreted (but version is correct).
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Payload size for Protocol error is zero
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#### Internal error
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Response in internal failure case.
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Payload size for Internal error is zero.
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