MRCI/docs/type_ids.md

3.1 Type IDs

All mrci frames transferred throughout this application have an 8bit numeric value to indicate the type of data being passed with the binary data. The type id enum values are as follows:

enum TypeID : quint8
{
    GEN_FILE              = 1,
    TEXT                  = 2,
    ERR                   = 3,
    PRIV_TEXT             = 4,
    IDLE                  = 5,
    HOST_CERT             = 6,
    FILE_INFO             = 7,
    PEER_INFO             = 8,
    MY_INFO               = 9,
    PEER_STAT             = 10,
    P2P_REQUEST           = 11,
    P2P_CLOSE             = 12,
    P2P_OPEN              = 13,
    BYTES                 = 14,
    SESSION_ID            = 15,
    NEW_CMD               = 16,
    CMD_ID                = 17,
    BIG_TEXT              = 18,
    TERM_CMD              = 19,
    HOST_VER              = 20,
    PRIV_IPC              = 21,
    PUB_IPC               = 22,
    PUB_IPC_WITH_FEEDBACK = 23,
    PING_PEERS            = 24,
    CH_MEMBER_INFO        = 25,
    CH_ID                 = 26,
    KILL_CMD              = 27,
    HALT_CMD              = 28,
    RESUME_CMD            = 29
};

3.2 Type Descriptions

TEXT This is text that can be displayed directly to the user, passed as command line arguments to be processed or used to carry text data within other data types.

format: [UTF-16LE_string] (no BOM)

GEN_FILE This is a file transfer type id that can be used to transfer any file type (music, photos, documents, etc...). It operates in its own protocol of sorts. The 1st GEN_FILE frame received by the host or client is TEXT parameters similar to what you see in terminal command lines with at least one of the arguments listed below. The next set of GEN_FILE frames received by the host or client is then the binary data that needs to be written to an open file or streamed until the limit defined in -len is meet.

The host or the client can be set as the sender or receiver of the GEN_FILE binary data. This designation is determined by what the command defined in genfile type when the NEW_CMD frame was sent. A genfile type of 2 sets the client as the sender and the host as the receiver. Genfile type 3 sets the client as the receiver and the host as the sender.

see section 3.3 for an example of how GEN_FILE works.

arguments:

• -len (int) | this is the integer value of the file size or amount of bytes to read/write.

• -offset (int) | this is a integer position that indicates where in the source or destination file to start reading/writing.

• -client_file (string) | this is the file path to the source/destination file in the client's file system.

• -remote_file (string) | this is the file path to the source/destination file in the host file system.

• -single_step | the presents of this argument tells both the client and host to operate in single step mode. single step mode causes the receiver of the binary data whether host or client to send an empty GEN_FILE frame after successfully receiving the data. this then tells the sender to send the next GEN_FILE frame containing binary data for the file and the cycle continues until len is meet. if this argument is not found, the sender can simply send all GEN_FILE data without waiting for an empty GEN_FILE from the receiver.

• -truncate | this indicates to whoever is the receiver to truncate the file being written to.

• -force | in some cases, the receiver might need to overwrite the target file. the presents of this argument tells it to overwrite without asking the user. the host should never send this argument and the client should ignore it if it is received from the host.

ERR This type id is similar to TEXT except it indicates that this is an error message that can be displayed directly to the user if needed.

PRIV_TEXT This id can be treated exactly like TEXT except this should tell the client to hide or do not echo the next TEXT data that the host is expecting, like a password or other sensitive text data.

BIG_TEXT Also formatted exactly like TEXT but this indicates to the client that this is a large body of text that is recommended to be word wrapped when displaying to the user. It can contain line breaks so clients are also recommended to honor those line breaks.

IDLE This doesn't carry any actual data, instead this indicates that the command id and branch id that sent it has finished it's task. Modules that send this doesn't need to terminate it's process.

KILL_CMD This doesn't carry any actual data, instead can be sent by the client or session object to tell the command-branch id sent in the frame to terminate the module process. Modules that receive this need to send a IDLE frame if a command is still running and then terminate itself. The module will have 3 seconds to do this before it is force killed by the session.

HALT_CMD This doesn't carry any actual data, instead can be sent by the client or session object to tell the command-branch id sent in the frame to pause/halt the current task that the command is currently running. All modules are not obligated to support this feature but highly recommended.

RESUME_CMD This is the other half of HALT_CMD that tells the module to resume the command task it was running.

HOST_CERT Just as the name implies, this data type is used by the host to send the host SSL certificate while setting up an SSL connection.

HOST_VER This data structure carries 3 numeric values that represent the host version as described in section 1.3.

  format:
  1. bytes[0-1] - version major (16bit little endian uint)
  2. bytes[2-3] - version minor (16bit little endian uint)
  3. bytes[4-5] - version patch (16bit little endian uint)

PRIV_IPC This is a data structure used to by modules to run async commands on the local session object only.

  format:
  1. bytes[0-1] - async command id (16bit little endian uint)
  2. bytes[2-n] - payload (data to be processed by async command)

PUB_IPC This is formatted exactly like PRIV_IPC except it is used by modules to run async commands on all peer session objects in the host while avoiding a run on the local session object.

PUB_IPC_WITH_FEEDBACK This has the same functionality as PUB_IPC except it is also feedback into the local session object.

FILE_INFO This is a data structure that carries information about a file system object (file,dir,link).

  format:
  1. bytes[0]     - flags (8bit little endian uint)
  2. bytes[1-8]   - creation time in msec since Epoch UTC (64bit little endian uint)
  3. bytes[9-16]  - modification time in msec since Epoch UTC (64bit little endian uint)
  4. bytes[17-24] - file size (64bit little endian uint)
  5. bytes[25-n]  - file name (UTF16-LE string, 16bit terminated)
  6. bytes[n-n]   - symmlink target if it is a symmlink (UTF16-LE string, 16bit terminated)

  notes:
  1. 16bit terminated UTF-16LE strings are basically
     terminated by 2 bytes of 0x00.
     
  2. the symmlink target is empty if not a symmlink but
     the terminator should still be present.

  flags:
  1. bit 0 - true if the object is a file
  2. bit 1 - true if the object is a directory
  3. bit 2 - true if the object is a symmlink
  4. bit 3 - true if the current user have read permissions
  5. bit 4 - true if the current user have write permissions
  6. bit 5 - true if the current user have execute permissions
  7. bit 6 - true if the object exist in the file system. if symmlink,
             this determines if the symm target exists or not.

PEER_INFO This carry some user account and session information about a peer client connected to the host.

  format:
  1. bytes[0-27]    28bytes  - session id (224bit hash)
  2. bytes[28-59]   32bytes  - user id (256bit hash)
  3. bytes[60-107]  48bytes  - user name (TEXT - padded with 0x00)
  4. bytes[108-235] 128bytes - app name (TEXT - padded with 0x00)
  5. bytes[236-299] 64bytes  - disp name (TEXT - padded with 0x00)

  notes:
  1. the session id is unique to the peer's session connection only. it
     can change upon reconnection.
     
  2. the user id is unique to the peer's user account. is stays constant
     even when the user name changes and across all clients logged into
     the same account.
     
  3. the display name is the preffered display name of the peer. clients
     are encouraged to use this rather than the user name when displaying
     peer info to the user. if empty, it's ok to just fall back to the user
     name.

PING_PEERS This is formatted extactly as PEER_INFO except it can be used the ASYNC_LIMITED_CAST async command to tell all peer sessions that receive it to send a PEER_INFO frame about you to their own clients and return PEER_INFO frames about themselves to you.

MY_INFO This contains all of the information found in PEER_INFO for the local session but also includes the following:

  format:
  1. bytes[300-427] 128bytes - email (TEXT - padded with 0x00)
  2. bytes[428-431] 4bytes   - host rank (32bit unsigned int)
  3. bytes[432]     1byte    - is email confirmed? (0x00 false, 0x01 true)

NEW_CMD This contains information about a new command that was added to the current session.

  format:
  1. bytes[0-1]     2bytes   - 16bit LE unsigned int (command id)
  2. bytes[2]       1byte    - 8bit LE unsigned int (genfile type)
  3. bytes[3-130]   128bytes - command name (TEXT - padded with 0x00)
  4. bytes[131-258] 128bytes - library name (TEXT - padded with 0x00)
  5. bytes[259-n]   variable - short text (16bit null terminated)
  6. bytes[n-n]     variable - io text (16bit null terminated)
  7. bytes[n-n]     variable - long text (16bit null terminated)

  notes:
  1. the genfile type is numerical value of 2, 3 or 0. a value of 2 
     indicates that the command handles/understands the GEN_FILE mini 
     protocol and it can be used to upload a file or other data to the 
     host. a value of 3 indicates the commmand downloads a file or other
     data from the host. 0 simply indicates that the command doesn't use
     or understand GEN_FILE.
     
  2. the library name can contain the module name and/or extra informaion 
     the client can use to identify the library the command is a part of.

CMD_ID This type id carries a 16bit unsigned LE int representing a command id.

format: 2bytes - 16bit LE unsigned int (command id)

CH_ID This type id carries a 64bit unsighed LE int indicating the channel id.

format: 8bytes - 64bit LE unsigned int (channel id)

SESSION_ID This is a fixed length 28byte(224bit) sha3 hash of a client's session id connected to the host. This is unique to just the client's tcp connection with the host. This can change upon re-connection.

format: 28bytes - session id (224bit sha3 hash)

PEER_STAT This contain status information of a peer client when the peer changes sub-channels or disconnects from the host.

  format:
  1. bytes[0-27]  28bytes - session id (224bit hash)
  2. bytes[28-81] 54bytes - channel-sub ids
  3. bytes[82]    1byte   - is disconnected? (0x00 false, 0x01 true)

  notes:
  1. if (is disconnected) is set true (0x01) the session id will no longer
     be valid for that peer client so you should not make anymore attempts
     to send data to it.
     
  2. channel-sub ids is a string of 9byte channel-sub id combinations at
     a fixed length of 54bytes (padded with 0x00). this indicates what
     channels-subs the peer currently have open if the peer's channel ids
     no longer match with your session, it can be considered inactive or
     disconnected since you will no longer send/receive data with this peer.

P2P_REQUEST This is formatted extactly like PEER_INFO except it is allowed to be sent directly to a peer session without retriction via the ASYNC_P2P async command. It will be up to the target peer to respond with a P2P_OPEN for the session to then unrestrict ASYNC_P2P so it will then be able to send/received other TypeIDs with this peer until P2P_CLOSE is sent/received. P2P_CLOSE can also be sent to decline the request.

P2P_OPEN This contains a 28byte session id hash of the peer session that you or the peer will allow direct communication with ASYNC_P2P.

format: 28bytes - session id (224bit sha3 hash)

P2P_CLOSE This is the other half of P2P_OPEN that will close direct communication with ASYNC_P2P.

format: 28bytes - session id (224bit sha3 hash)

BYTES This contains arbitrary binary data of any format.

CH_MEMBER_INFO This contains public information about a channel member.

  format:
  1. bytes[0-7]  8bytes   - channel id (64bit unsigned int)
  2. bytes[8-39] 32bytes  - user id (256bit hash)
  3. bytes[40]   1byte    - is invite? (0x00=false, 0x01=true)
  4. bytes[41]   1byte    - member's channel privilege level (8bit unsigned int)
  5. bytes[42-n] variable - user name (TEXT - 16bit null terminated)
  6. bytes[n-n]  variable - display name (TEXT - 16bit null terminated)
  7. bytes[n-n]  variable - channel name (TEXT - 16bit null terminated)
  
  notes:
  1. a 16bit null terminated TEXT formatted string ended with 2 bytes of
     (0x00) to indicate the end of the string data.
     
  2. the member's privilege level can be any of the values discribed in
     section [4.3](host_features.md).
     
  3. is invite? indicates if this user has received an invite to join
     that channel by has not accepted yet. if, accepted the user will
     become a full member of the channel at the level indicated by this
     data type.

3.3 GEN_FILE Example

Setup:

• The host has a command called upload_file with a command id of 768 and handles the GEN_FILE data type with a genfile type of 2.
• The client has a file called /home/foo/bar.mp3 and wants to upload it to the host file /home/host/music/bar.mp3 and the client knows the file size is 512bytes.

Process:

To upload the file, the client calls command id 768 with the following text arguments (must still be sent as a GEN_FILE): -client_file "/home/foo/bar.mp3" -remote_file "/home/host/music/bar.mp3" -len 512

The host can then return text arguments to the client like (also sent as a GEN_FILE): -truncate and/or -single_step

This only needs to be done if the command call needs to be modified by host and if the client supports such a thing. In this example, host will just return an empty GEN_FILE because there is no need for modification.

At this point, the host will then need to check of the destination file: /home/host/music/bar.mp3 already exists. If it does, the host will need to ask the user if it's ok to overwrite.

Once the host confirms it is ok to write to the destination file, it will then need to send another empty GEN_FILE to the client to confirm that it is ready to start receiving GEN_FILE frames from the client through command id 768 that will contain binary data to be written to the destination file until -len (512 bytes) is meet.