The questions

A task does not run on its own: while it does, STN asks the app eighteen questions and the app answers them. Is this user logged in? What bytes does this task send? What did the answer mean? What is the device's network? — and the rest. Every platform funnels all eighteen through one thing:

your app is	what answers them
Rust	impl App for MyApp, given to stn.set_callback(MyApp)
iOS / watchOS, Swift or Objective-C	one closure given to MarsStn.setApp { … }, or the block [MarsStn setApp:] takes
Android, Kotlin or Java	StnLogic.ICallBack, given to StnLogic.setCallBack(…)
Kotlin Multiplatform	one ask, given to StnLogic.setApp { … }
anything with a C FFI	one function pointer, given to mars_stn_set_app(ctx, ask)
HarmonyOS	the same function pointer, through a NAPI shim of your own

The names are the ones the C++ project used, so an answer written there is written here — all eighteen of them, in the order STN numbers them:

#	the question	what STN wants	Rust	Swift	shared Kotlin	Android	C
1	makesureAuthed	whether this user is logged in	makesure_authed	.makesureAuthed	Question.Kind.MakesureAuthed	makesureAuthed	MarsStnQuestionMakesureAuthed
2	trafficData	how much went out and came in	traffic_data	.trafficData	Question.Kind.TrafficData	trafficData	MarsStnQuestionTrafficData
3	onNewDns	the addresses of a host	on_new_dns	.onNewDns	Question.Kind.OnNewDns	onNewDns	MarsStnQuestionOnNewDns
4	onPush	the server sent this, and no task asked for it	on_push	.onPush	Question.Kind.OnPush	onPush	MarsStnQuestionOnPush
5	req2Buf	the bytes the task sends	req2buf	.req2Buf	Question.Kind.Req2Buf	req2Buf	MarsStnQuestionReq2Buf
6	buf2Resp	what the answer meant	buf2resp	.buf2Resp	Question.Kind.Buf2Resp	buf2Resp	MarsStnQuestionBuf2Resp
7	onTaskEnd	what to do about the end	on_task_end	.onTaskEnd	Question.Kind.OnTaskEnd	onTaskEnd	MarsStnQuestionOnTaskEnd
8	reportConnectStatus	the network, as the app is to see it	report_connect_status	.reportConnectStatus	Question.Kind.ReportConnectStatus	reportConnectInfo	MarsStnQuestionReportConnectStatus
9	onLongLinkNetworkError	the main long link failed	on_long_link_network_error	.longLinkNetworkError	Question.Kind.LongLinkNetworkError	—	MarsStnQuestionLongLinkNetworkError
10	onShortLinkNetworkError	a short link failed	on_short_link_network_error	.shortLinkNetworkError	Question.Kind.ShortLinkNetworkError	—	MarsStnQuestionShortLinkNetworkError
11	onLongLinkStatusChange	where the default long link is	on_long_link_status_change	.longLinkStatusChange	Question.Kind.LongLinkStatusChange	—	MarsStnQuestionLongLinkStatusChange
12	getLonglinkIdentifyCheckBuffer	the check a new link is used with	identify_check_buffer	.identifyCheckBuffer	Question.Kind.IdentifyCheckBuffer	getLongLinkIdentifyCheckBuffer	MarsStnQuestionIdentifyCheckBuffer
13	onLonglinkIdentifyResponse	whether the answer is the one the check asked for	identify_response	.identifyResponse	Question.Kind.IdentifyResponse	onLongLinkIdentifyResp	MarsStnQuestionIdentifyResponse
14	requestSync	the app is asked to sync	request_sync	.requestSync	Question.Kind.RequestSync	requestDoSync	MarsStnQuestionRequestSync
15	requestNetCheckShortLinkHosts	the hosts the network check may probe	net_check_shortlink_hosts	.netCheckShortLinkHosts	Question.Kind.NetCheckShortLinkHosts	requestNetCheckShortLinkHosts	MarsStnQuestionNetCheckShortLinkHosts
16	reportTaskProfile	everything a task left behind	report_task_profile	.reportTaskProfile	Question.Kind.ReportTaskProfile	reportTaskProfile	MarsStnQuestionReportTaskProfile
17	reportTaskLimited	a task the two gates refused: which gate, and its reading	report_task_limited	.reportTaskLimited	Question.Kind.ReportTaskLimited	—	MarsStnQuestionReportTaskLimited
18	reportDnsProfile	how a dns question went	report_dns_profile	.reportDnsProfile	Question.Kind.ReportDnsProfile	—	MarsStnQuestionReportDnsProfile

A question the app does not answer is a question with the default answer, and every platform but Android carries one for all eighteen — so an app writes the ones it cares about: default: return .nothing() in Swift, else -> Answer.None in the shared Kotlin, an App with three methods in Rust.

In Rust, two of the eighteen are asked of the app only for a task nobody is awaiting: the body you hand stn.send(task, body) is what req2buf would have been asked for, and the bytes the server answers with are what buf2resp would have been handed — both are kept for the Sent instead. Every other question is asked the same way, on_task_end included, and all eighteen are asked of the app for a task nobody awaits. See the task.

Android's ICallBack is the plain interface the C++ project's Java declared, and it has no defaults: the object is the app's to finish. It is asked thirteen of the eighteen — the five marked — above are ones the Java api has no method for, so STN takes its own answers for them — plus one of its own, isLogoned, which nothing asks.

marsrs-kmp's shared Kotlin is asked all eighteen on Kotlin/Native and thirteen on Android, the same five.

reportTaskLimited is the one question only a refused task is asked for: the two anti-avalanche gates weigh every task that goes out, and a task they refuse never reaches a queue, so nothing else the app hears carries it. What the app is handed is which gate refused it and the reading it weighed the task against — how long ago the same body went out, or how many bytes the funnel would not take — and what it answers is that reading, changed or not. The reading is limit on the question, and Answer.Limit or .limit(…) is how the shared Kotlin and Swift hand it back; in C it is the limit of MarsStnQuestion and a MarsStnAnswerLimit.

That answer is a report and not an override: the C++'s own is void, and a gate's refusal stands whatever an app writes into it — a task the gates refused stays refused and ends with LOCAL_ANTI_AVALANCHE. What the port does with the answer is nothing at all, which is the same thing: anti_avalanche_check asks and drops it, so no answer of an app's lets a refused task out. See the long link for the link a task goes out on.

The account and the device are not one of the eighteen: on Android they are AppLogic.ICallBack, and on every other platform they are nothing STN asks about.

The boot, on Android

Android is the one platform where the app also starts the bridges and hands over what STN asks about the device:

Mars.init(context, Handler(Looper.getMainLooper()))
Mars.onCreate(true)

AppLogic.setCallBack(object : AppLogic.ICallBack { /* the account and the device */ })
StnLogic.setCallBack(object : StnLogic.ICallBack { /* the thirteen it is asked, and `isLogoned` */ })

// when the screen or the network changes
BaseEvent.onForeground(true)
BaseEvent.onNetworkChange()

AppLogic is the account and the device; BaseEvent is the screen and the network. The screen and the network are two an app reports on every platform — under the name that platform spells them with, which the long link lists. What is Android's alone is the boot: Mars.init and Mars.onCreate.

Where to go next

• The task — what a task is made of, and how one ends.
• The long link — the connection an app keeps up.
• Getting started — the dependency and a running task, on every platform that carries STN.