Error codes

A failed request gets {"janus":"error","error":{"code":N,"reason":"..."}}. The codes are the ones of the C server (apierror.h). The reason strings follow the C server's too; the replay scenarios check them for every code they provoke.

Code	Name	Raised when
403	Unauthorized	Wrong or missing apisecret, token or admin_secret.
405	Unauthorized plugin	The token does not allow this plugin.
450	Transport specific	The transport refused it (for example HTTP with a method it does not take).
452	Missing request	A request with no request member where one is needed.
453	Unknown request	The janus value is not known on this path (on the base path the server answers 457).
454	Invalid JSON	The body does not parse; the reason carries the parser's message.
455	Invalid JSON object	Parsed, but not an object.
456	Missing mandatory element	A required member is missing, for example transaction or plugin.
457	Invalid request path	The request is not valid at this path.
458	Session not found	The session id is unknown or was destroyed.
459	Handle not found	The handle id is unknown in this session.
460	Plugin not found	attach named a plugin that is not loaded.
461	Plugin attach	The plugin refused the attach.
462	Plugin message	The plugin could not take the message.
463	Plugin detach	The plugin failed to detach.
464	JSEP unknown type	jsep.type is not offer, answer and so on.
465	JSEP invalid SDP	The SDP does not parse or is missing mandatory lines.
466	Trickle invalid stream	The candidate names a stream or m-line that does not exist.
467	Invalid element type	A member has the wrong JSON type.
468	Session conflict	A session with this id exists.
469	Unexpected answer	An answer arrived without an offer pending.
470	Token not found	Admin token request names an unknown token.
471	WebRTC state	The request does not fit the PeerConnection's state.
472	Not accepting sessions	create while the server is draining (accept_new_sessions set to false).
490	Unknown / unsupported	Anything else. In this port also: an Admin request the build does not support, such as query_transport.

Plugin errors are not Janus errors

A plugin reports its own errors inside a normal success or event: plugindata.data.error_code and plugindata.data.error. Each plugin has its own error codes, listed on the plugin pages. A client has to check both levels.

{
  "janus": "success",
  "plugindata": {
    "plugin": "janus.plugin.videoroom",
    "data": { "videoroom": "event", "error_code": 429, "error": "Missing mandatory element (room)" }
  }
}

That reply is a real one from the binary (see the last exchange of the walkthrough).