# Client-Server Protocol

Protocol version: <b>"0.3"</b>

Every json message must be minimized (i.e. must not contain newlines) and be followed by a newline. This rule makes receiving and parsing the messages easier because you can read until a newline comes and you will parse every json message seperately because you won't read multiple json messages from the buffer at a time.

## 1. Start a connection

To start a connection you have to check the versions and verify the login or signup.
Only if step 1.1 and 1.2 have been accomplished a usable connection is negotiated.
You can close the connection by sending a cancel message.

### 1.1 Version check
Client:
```
{
	"major": int,
	"minor": int
}
```
(For example, if the version number is 42.1, then major is 42, minor is 1.)

Server:
```
{
	"major": int,
	"minor": int,
	"accept": bool
}
```

If `accept` is `true` the connection is valid. Else the connection will be terminated after the server answered.


## 1.2 Login / Signup

The client is supposed to always send every field used for the login requests: `login`, `user`, `pass` and `cancel`.
The server is supposed to always send every field used for the login answer: `accept` and `error`.

### 1.2.1 Login
Client:
```
{
	"login": true,
	"user": string,
	"pass": string,
	"cancel": false
}
```

Server:
```
{
	"accept": bool,
	"error": string
}
```

If `accept` is `true` the connection is valid and the user is logged in. Else `error` has an error string and the connection will be terminated after the server answered.

### 1.2.2 Signup
Client:
```
{
	"login": false,
	"user": string,
	"pass": string,
	"cancel": false
}
```

Server:
```
{
	"accept": bool,
	"error": string
}
```

If `accept` is `true` the connection is valid and the user is logged in and signed up. Else `error` has an error string and the connection will be terminated after the server answered.

### 1.2.3 Cancel login
Client:
```
{
	"login": bool,
	"user": string,
	"pass": string,
	"cancel": true
}
```

After the cancel message was sent the connection will be closed.


## 2. Sending commands

Commands can be sent by the client after a connection has been negotiated (See 1).
Commands can be used unrelated to each other.

### 2.1 Status command
Client:
```
{
	"command": "status"
}
```

Server:
```
{
	"command": "status",
	"response": string
}
```

### 2.2 List command
List is split in two commands. `list` to request a list download and `listdata` to download the list.

#### 2.2.1 list - request file list download
Client:
```
{
	"command": "list"
}
```
Server:
```
{
	"command": "list",
	"accept": bool,
	"items": int,
	"chunks": int,
	"error": string
}
```
`chunks` is the number of chunks that will be sent.

#### 2.2.2 listdata - download file list
Client:
```
{
	"command": "listdata",
	"chunk": int,
	"cancel": bool
}
```
Here `chunk` is the number of remaining chunks. (Thus, when requesting the first chunk the number of chunks - 1 is expected.)
<br /><br />
Server:
```
{
	"command": "listdata",
	"remaining": int,
	"cancel": bool,
	"names": string[],
	"error": string
}
```
The client has to request every chunk until all names have been sent and `remaining` hits `0`.


### 2.3 Put command

Put is split in two commands. `put` to request a file upload and `putdata` to upload the data.

#### 2.3.1 put - request upload
Client:
```
{
	"command": "put",
	"file": string,
	"size": int,
	"chunks": int
}
```
`chunks` is the number of chunks of the file to send.
<br /><br />
Server:
```
{
	"command": "put",
	"file": string,
	"accept": bool,
	"error": string
}
```
If `accept` is `true` the connection is valid and the client can start sending the file. Else the put request was rejected and is hereby canceled. `error` should contain an error string if the request was rejected.


#### 2.3.2 putdata - upload data
Client:
```
{
	"command": "putdata",
	"file": string,
	"data": string,
	"remaining": int,
	"cancel": bool
}
```
`data` is a base64 string and contains a piece of the file. The client will loop this until the file is completely sent and the server has to send and received message for every chunk.
`remaining` is a counter how many chunks will follow and the transfer is over after it hits `0`.
If `cancel` is `true` the file transfer will be canceled.
<br /><br />
Server:
```
{
	"command": "putdata",
	"file": string,
	"recieved": int,
	"cancel": bool,
	"error": string
}
```
If `cancel` is `true` then the upload of the file is canceled and an error message should be in `error`. <br />
Note that `received` is the number of remaining (!!!) chunks, here the server responds with the `remaining` value originally sent in the request.

### 2.4 Get command

Get is split in two commands. `get` to request a file download and `getdata` to download the data.

#### 2.4.1 get - request download

Client:
```
{
	"command": "get",
	"file": string
}
```

Server:
```
{
	"command": "get",
	"file": string,
	"accept": bool,
	"chunks": int,
	"error": string
}
```
If `accept` is `true` the connection is valid and the server can start sending the file. Else the get request was rejected and is hereby canceled. `error` should contain an error string if the request was rejected. `chunks` is the number of chunks of the file.

#### 2.4.2 getdata - download data

Client:
```
{
	"command": "getdata",
	"file": string,
	"chunk": int,
	"cancel": bool
}
```

Here `chunk` is a counter how many chunks will follow. (Thus, when requesting the first chunk, the number of chunks - 1 is expected.)
If `cancel` is `true` then cancel the download of the file.
<br /><br />
Server:
```
{
	"command": "getdata",
	"file": string,
	"data": string,
	"remaining": int,
	"cancel": bool,
	"error": string
}
```
`data` is a base64 string and contains a piece of the file. The client must request every chunk.
`remaining` is a counter how many chunks will follow (so it equals the `chunk` value originally sent in the request) and the transfer is over after it hits `0`.
If `cancel` is `true` then the download of the file is canceled and an error message should be in `error`.

### 2.5 Head command

The `head` command requests the first 32 bytes of `file` from the server for further inspection by the client. If the file is smaller than 32 bytes, the first 4 bytes are sent instead. If the file is even too small for this, `data` stays empty, and an error is sent.

Client:
```
{
	"command": "head",
	"file": string
}
```

Server:
```
{
	"command": "head",
	"accept": bool,
	"file": string,
	"data": string,
	"error": string
}
```
`data` is a base64 encoded string containing the requested bytes of the file.

### 2.6 Deleteme command

The `deleteme` command allows a logged in user to delete their account on the server. This action needs to be confirmed with the users password.

Client:
```
{
	"command": "deleteme",
	"pass": string
}
```

Server:
```
{
	"command": "deleteme",
	"accept": bool,
	"error": string
}
```
If `accept` is true the user has been deleted and the connection will be closed by the server.

### 2.7 Deletefile

The `deletefile` command deletes a file from the server if its allowed to in config.

Client:
```
{
	"command": "deletefile",
	"file": string
}
```

Server:
```
{
	"command": "deletefile",
	"file": string,
	"accept": bool,
	"error": string
}
```

### 2.8 Notifications

The `notifications` command allows the logged in user to get a list of notifications since the last time.

Client:
```
{
	"command": "notifications"
}
```

Server:
```
{
	"command": "notifications",
	"accept": bool,
	"messages": string[], 
	"error": string
}
```

### 2.9 ExtendedStatus

The `extendedstatus` command allows the client to request detailed information about ongoing transfers at the server.

Client:
```
{
	"command": "extendedstatus"
}
```

Server:
```
{
    "command": "extendedstatus",
    "accept": bool,
    "error": string,
    "transfersclientserver": {
        "upload": bool,
        "file": string,
        "progress": int
    }[],
    "transfersserverserver": {
        "type": string,
        "file": string,
        "progress": int,
        "speed": float,
        "method": string
    }[]
}
```
The answer consists of an array of objects, each representing a transfer. <br />
In case of client-server transfers, `upload` indicates wether the transfer is an up- or download. In case of server-server transfers, `type` indicates wether the file  is `upload`ing, `download`ing or `queued` for upload. <br />
`file` contains the name of the file being transferred. <br />
`progress` contains the percentage completed. <br />
`speed` contains the speed in bytes per second. <br />
`method` contains the covert channel method being used.

### 2.10 Queue command

To add a file that is already on the server to the queue for sending with the covert channel, the client uses the `queue` command.

Client:
```
{
	"command": "queue",
	"file": string
}
```

Server:
```
{
	"command": "queue",
	"file": string,
	"accept": bool,
	"error": string
}
```

### 2.11 Dequeue command

To remove a file from the queue for sending with the covert channel, the client uses the `dequeue` command.

Client:
```
{
	"command": "dequeue",
	"file": string
}
```

Server:
```
{
	"command": "dequeue",
	"file": string,
	"accept": bool,
	"error": string
}
```
### 2.12 Extendedlist command
Extendedlist is split in two commands. `extendedlist` to request a list download and `extendedlistdata` to download the list.

#### 2.12.1 extendedlist - request file list download
Client:
```
{
	"command": "extendedlist"
}
```
Server:
```
{
	"command": "extendedlist",
	"accept": bool,
	"items": int,
	"chunks": int,
	"error": string
}
```
`chunks` is the number of chunks that will be sent.

#### 2.12.2 extendedlistdata - download file list
Client:
```
{
	"command": "extendedlistdata",
	"chunk": int,
	"cancel": bool
}
```
Here `chunk` is the number of remaining chunks. (Thus, when requesting the first chunk the number of chunks - 1 is expected.)
<br /><br />
Server:
```
{
	"command": "extendedlistdata",
	"remaining": int,
	"cancel": bool,
	"files": {
        "name": string,
        "head": string,
        "size": float
    }[],
	"error": string
}
```
The client has to request every chunk until all names have been sent and `remaining` hits `0`. <br />
The list contains the name of a file and the `head` as specified by the `data` field of the head command (section 2.5), and its `size` in kByte.


## 3. Close connection

### 3.1 Close command

Client:
```
{
	"command": "close"
}
```


Server:
```
{
	"command": "close",
	"response": "bye"
}
```