All communication consists of messages that are one line of human-readable UTF-8 text optionally followed by a single newline and binary data. The protocol is not a request-response one. Messages may be sent in either direction at any time, either in response to some message, or spontaneously. For 'tile' messages, the client may send a bunch of tile requests without waiting for return messages. The server may send tiles proactively (guessing what the client might need). Etc. client -> server ================ canceltiles All outstanding tile messages from the client to the server are dropped and will not be handled. There is no guarantee of exactly which tile: messages might still be sent back to the client. disconnect [reason] Sent before disconnecting gracefully. reason: optional human-readable reason to disconnect. downloadas downloadas name= id= format= options= Exports the current document to the desired format and returns a download URL The id identifies the request on the client. getchildid Requests the child id so that it knows where the files needs to be sent when it is inserted in the document gettextselection mimetype= Request selection's content paste mimetype= Paste content at the current cursor position. insertfile name= type= Inserts the file with the name into the document, we currently support type = 'graphic' invalidatetiles part= tileposx= tileposy= tilewidth= tileheight= All parameters are numbers. Makes the server remove any cached tiles intersecting with the given area (in twips). key type= char= key= is 'input' or 'up', and are numbers. load Deprecated. load [part=] url= [timestamp=] [options=] part is an optional parameter. is a number. timestamp is an optional parameter. is provided in microseconds since the Unix epoch - midnight, January 1, 1970. options are the whole rest of the line, not URL-encoded loolclient Upon connection, a client must announce the version number it supports. Major: an integer that must always match between client and server, otherwise there are no guarantees of any sensible compatibility. This is bumped when API changes. Minor: an integer is more flexible and is at the discretion of either party. Security fixes that do not alter the API would bump the minor version number. Patch: an optional string that is informational. mouse type= x= y= count= is 'buttondown', 'buttonup' or 'move', others are numbers. renderfont font= requests the rendering of the given font. The font parameter is URL encoded requestloksession requests the initialization of a LOK process in an attempt to predict the user's interaction with the document resetselection saveas url= format= options= is a URL, encoded. is also URL-encoded, i.e. spaces as %20 and it can be empty options are the whole rest of the line, not URL-encoded, and can be empty selecttext type= x= y= is 'start', 'end' or 'reset', and are numbers. selectgraphic type= x= y= is 'start' or 'end' and are numbers. status styles tile part= width= height= tileposx= tileposy= tilewidth= tileheight= All parameters are numbers. unload [save|force] unloads the document. if 'save' is specified, the document is saved before unloading, otherwise, changes are discarded. if other users have the document open, and save not specified, 'force' is necessary to discard changes. uno is a line of text. partpagerectangles Invokes lok::Document::getPartPageRectangles(). clientvisiblearea x= y= width= height= Invokes lok::Document::setClientVisibleArea(). server -> client ================ loolserver Upon connection, the server must announce the version number it supports. Major: an integer that must always match between client and server, otherwise there are no guarantees of any sensible compatibility. This is bumped when API changes. Minor: an integer is more flexible and is at the discretion of either party. Security fixes that do not alter the API would bump the minor version number. Patch: an optional string that is informational. downloadas: jail= dir= name= port= The client should then request http://server:port/jail/dir/name in order to download the document error: cmd= kind= [code=] is the command part of the corresponding client->server message that caused the error. is some single-word classification

 (when provided) further specifies the error as forwarded from
    LibreOffice

getchildid: id=

    Returns the child id

invalidate: part= x= y= width= height=

    All parameters are numbers. Tells the client to invalidate any
    cached tiles for the document area specified (in twips), at any
    zoom level.

    The client should handle either this message or the
    invalidatetiles: message, which has a different syntax, with
    payload directly from the LOK_CALLBACK_INVALIDATE_TILES
    callback. (The latter does not contain a part number, and as the
    protocol is asynchronous, it is unclear whether a client can be
    sure, or find out with certainty, for what part the
    invalidatetiles: message is. The invalidatetiles: message will be
    dropped soon.)

nextmessage: size=

     is the size, in bytes, of the next message, in case it
    is "large". (In practice, nextmessage: messages precede each tile:
    message). Can be ignored by clients using an API that can read
    arbitrarily large buffers from a WebSocket (like JavaScript), but
    must be handled by clients that cannot (like those using Poco
    1.6.0, like the "loadtest" program in the loolwsd sources).

status: type= parts= current= width= height= [partNames]

     is 'text, 'spreadsheet', 'presentation', 'drawing' or 'other. Others are numbers.
    if the document has multiple parts and those have names, part names follow separated by '\n'

styles: {"styleFamily": ["styles in family"], etc. }

partpagerectangles: 

    Payload format is the same as LOK_CALLBACK_TEXT_SELECTION.

textselectioncontent: 

    Current selection's content

tile: part= width= height= tileposx= tileposy= tilewidth= tileheight=


    The parameters from the corresponding 'tile' command.

Each LOK_CALLBACK_FOO_BAR callback causes a corresponding message to
the client, consisting of the FOO_BAR part in lowercase, without
underscore, followed by a colon, space and the callback payload. For
instance:

invalidatecursor:

invalidatetiles: 

The communication between the parent process (the one keeping open the
Websocket connections to the clients) and a child process (handling
one document through LibreOfficeKit) uses the same protocol, with
the following additions and changes:

unocommandresult: 

Callback that an UNO command has finished.
See LOK_CALLBACK_UNO_COMMAND_RESULT for details.

child -> parent
===============

child 

    Must be the first message sent from the child to the parent. The
    parent has passed the id (a 64-bit random number) to the child
    when starting it, so this is how the child identificates itself.

curpart: part=

    Sent to the parent process before certain messages that the parent
    needs to act on in addition to passing them on to the client, like
    invalidatetiles:

nextmessage: size=

    each tile: message sent from the child to the parent is preceded
    by a nextmessage: message that gives an upper limit on the size of
    the tile: message that will follow. (We assume it is only tile:
    messages that can be "large".) Once we depend on Poco 1.6.1, where
    one doesn't need to use a pre-allocated buffer when receiving
    WebSocket messages, this will go away.

saveas: url=

     is a URL of the destination, encoded. Sent from the child to the
    parent after a saveAs() completed.