Core API

This page refers to the future version 2.0.0 of TapTo which is in active development. Please don't use any information on this page until it's been finalised and released.

The TapTo API is an API available on and published by every device running the core TapTo software. This API allows management of all TapTo features which would not present a security risk. The TapTo Life app uses this API for all communication with TapTo devices, as does most of the arguments when TapTo is run via the CLI.

This page documents the protocol used to communicate with the API and each method available to interact with a TapTo device. It is the source of truth when developing applications that interact with TapTo.

Communication Protocol

The API uses a standard WebSocket connection to exchange JSON payloads using a custom variant of the JSON-RPC 2.0 protocol. It is not compatible with standard JSON-RPC libraries.

All remote unsecured WebSocket connections must encrypt every payload using the secure layer detailed below, or else the payload will be immediately rejected. Local cleartext (unencrypted) connections are allowed, depending on the platform and privilege context of the running service.

Communication follows a loose client-server relationship. Clients, by default, are not expected to implement the API beyond what that particular client needs to function.

Connection

Connections to the API can be established with any standard WebSocket client, using the root endpoint (/) of the HTTP server published by the TapTo service. By default, the HTTP server is accessible on port 7497. Keep in mind this port is configurable by the user.

An example address for connecting to the API: ws://10.0.0.123:7497/

The connection requires no special configuration or authentication to begin.

JSON Payloads

Server and clients communicate back and forth using JSON payloads and a request-response based on the JSON-RPC 2.0 protocol. The TapTo protocol is incompatible with existing JSON-RPC libraries. See Differences From JSON-RPC for details.

Because a WebSocket connection is asynchronous, request payloads are tagged with a unique ID. The client must keep track of IDs sent to another client and wait for a matching response object.

Requests

A request object asks the connected server to run a pre-defined method, and report back when it's completed with a response object.

An example request:

{
    "tapto": 1,
    "id": "9ab7679f-6de9-11ef-9a9b-020304050607",
    "timestamp": 1725803556229,
    "method": "media.search",
    "params": {
        "query": "240p"
    }
}

This request would query TapTo's media database for a file containing the word "240p" and return a response with the search results.

Request keys:

Key	Type	Required	Description
tapto	number	Yes	Specifies the protocol version and is used to validate a payload. It must be contained in every request or else the request will be rejected. Currently this must be the integer 1.
id	string	Yes*	A UUID v4 generated by the requesting client, used to match requests back to responses. A request missing this key is valid but would be treated as a notification and not receive any response (or an error).
timestamp	number	Yes	An integer timestamp of the current UNIX epoch in milliseconds when the request was generated. This value is used by the secure layer to validate the request.
method	string	Yes	A string corresponding to a method to be run by the receiving server.
params	any	No	Arguments supplied for the method. The value of this key depends on the method used and is omitted for some methods.

All available request methods and their parameters are documented below.

Notifications

Notifications are requests which do not contain an ID. Otherwise, they are identical to a standard request object. Notifications can be sent by either server or client and do not receive a response.

Like standard requests, notifications may or may not have parameters and its value will depend on the method. Types of notifications are documented below.

Responses

Every request sent must have a matching response. An example response to the media.search request shown above:

{
    "tapto": 1,
    "id": "9ab7679f-6de9-11ef-9a9b-020304050607",
    "timestamp": 1725803557,
    "result": {
        "results": [{
            "system": {
                "id": "Gameboy",
                "name": "Gameboy"
            },
            "name": "240p Test Suite (PD) v0.03 tepples",
            "path": "Gameboy/240p Test Suite (PD) v0.03 tepples.gb"
        }],
        "total": 1
    }
}

Response keys:

Key	Type	Required	Description
tapto	number	Yes	Same as a request.
id	string	Yes	Same as a request. The same ID sent by the original request.
timestamp	number	Yes	Same as a request, with an updated time.
result	any	No*	Return value of the method. May be null depending on the method. See methods for possible values.
error	Error	No*	If a method failed, this key will be populated with the error details and the result key will be empty. See below for details about errors.

Response Errors

If a method fails, it will populate the error key in the response object with details about the failure. An example of a failed request:

{
    "tapto": 1,
    "id": "9ab7679f-6de9-11ef-9a9b-020304050607",
    "timestamp": 1725805903,
    "error": {
        "code": 1,
        "message": "query or system is required"
    }
}

Error keys:

Key	Type	Required	Description
code	number	Yes	An integer specifying the general error category. Error codes are not yet formalised.
message	string	Yes	Short human readable message explaining the error cause if possible.

Protocol Errors

If a low-level error occurs before a request context can be established, a protocol error will be sent back. This can happen, for example, if a JSON payload is malformed or a payload could not be decrypted. They're identical to an error response except they will have no ID.

Protocol errors may be sent cleartext if a secure context couldn't be established.

Secure Layer

The API supports a secure layer when communicating via an insecure WebSocket connection. This layer is required for all insecure remote WebSocket connections, and payloads will be rejected if not encrypted.

Encryption is performed using AES256 and a shared secret key held by both server and client which is exchanged outside the API. Each payload sent must be encrypted by the sender and decrypted by the receiver. Responses must also be encrypted.

Be aware that although this process authenticates a client, TapTo does not currently enforce any type of role-based access. Any client with a valid secret key must be trusted with full access to the API.

An encrypted payload is in the format: tapto:<client id>:<base64 encoded data>

The client ID is matched back to the TapTo service's internal database of IDs and associated secret keys. If there's a match, it will attempt to decrypt the encrypted data.

Clients are also managed through the API, but can only be done so via a device-local connection.

Each client must have accurate time set, as the timestamp is validated on the receiving server and checked against a history of payloads.

If a payload is decrypted successfully, it continues through the standard protocol process until the response which will be encrypted before sending back.

Anonymous Access

Anonymous cleartext access is, generally, allowed when an API connection is made from a loopback address (i.e. from the same device TapTo is running). This access depends on the platform and whether the service is running with elevated privileges. Check the page for the specific platform you're using to make sure it's available to you.

This access is also allowed when a connection is made over a WebSocket Secure (wss) connection.

Launch Endpoint

The HTTP server has one other endpoint which allows restricted access to trigger generic launch methods using a GET request. This endpoint is specifically meant to support uses such as QR codes scanned by a phone.

The endpoint is: /l/

An example request: GET http://10.0.0.123:7497/l/**launch.system:snes

This would act as though a token with the text **launch.system:snes had been scanned, depending on this text being explicitly allowed in the config file.

Differences From JSON-RPC

There are three differences from JSON-RPC 2.0 in the variant used by the TapTo API:

• The jsonrpc key no longer exists on payloads, to signal incompatibility with existing libraries.
• A new tapto key has been added to all payloads, which must currently be set to the number 1.
• A new timestamp key has been added to all payloads, which must be set to the UNIX epoch timestamp in milliseconds of the time the payload is sent.

Otherwise, the protocol used by TapTo is identical to JSON-RPC 2.0 and can be assumed as such. Any future changes will be shown by an increment of the tapto key number.

Methods

Methods are used to execute actions and request data back from the API.

Notifications

Notifications let a server or client know an event has occurred.

Reader

readers.connected

A new reader was connected to the server.

readers.disconnected

A connected reader was disconnected from the server.

Tokens

tokens.launching

A new token was added to the launch queue.

tokens.active

The state of the currently active token has changed.

Media

media.started

New media was started on server.

media.stopped

Media has stopped on server.

media.indexing

The state of the indexing process has changed.