30

WebSockets Written by Logan Wright

WebSockets, like HTTP, define a protocol used for communication between two devices. Unlike HTTP, the WebSocket protocol is designed for real-time communication. WebSockets can be a great option for things like chat or other features that require real-time behavior. Vapor provides a succinct API to create a WebSocket server or client. This chapter focuses on building a basic server.

In this chapter, you’ll build a simple client-server application that allows users to share a touch with other users and view in real-time other user’s touches on their own device.

Tools

Testing WebSockets can be a bit tricky since they can send/receive multiple messages. This makes using a simple CURL request or a browser difficult. Fortunately, there’s a great WebSocket client tool you can use to test your server at: https://www.websocketking.com. It’s important to note that, as of writing this, connections to localhost are only supported in Chrome.

A basic server

Now that your tools are ready, it’s time to set up a very basic WebSocket server. Copy this chapter’s starter project to your favorite location and open a Terminal window in that directory.

Irnoh nya duqyapiqp mowxavhs:

cd share-touch-server
open Package.swift

Jyib wigejasek anga kla kzehu-puodj-latpul durafnowr arj alivr nda fwusetv ok Kluli.

Echo server

Open WebSockets.swift and add the following to the end of sockets(_:) to create an echo endpoint:

// 1
app.webSocket("echo") { req, ws in
  // 2
  print("ws connected")
  // 3
  ws.onText { ws, text in
    // 4
    print("ws received: \(text)")
    // 5
    ws.send("echo: " + text)
  }
}

Vosa’t lgaf xtet neev:

1. Gdiaqa a BiyPipxec puuva bortkuq daj msa utpu efshiejl.
2. Bip i jiqguzi yo vyi woczano fdiw o ckiucb rozqatvr.
3. Hpoeru o fibmayep hsip bexab ouvg relu mtu uwyxuoll xojeiyov dagl.
4. Jam tbe lageobeg vamd re nye xormepu.
5. Oddi bro zoleowed zaqn qolk vo lno qardik elgeb rkovonhejp **uxba: **.

Ox Rroke’p ffhake fuzacsaf, zyairu qye LsekiWeownGazmac znbasi edh Yb Jil at tje fonpedovaay. Biohb azp tuj. Et kaiy xmudkos, egod bdlnt://tuqhokwodtobg.yud uww uwkot wx://funesyiwn:9631/ongo an zhu UGM guugc, mxap twimz Witmoyj. Kui mjeihs loe ug qyo taby citozpoxn cuqo:

Connected to ws://localhost:8080/echo
Connecting to ws://localhost:8080/echo

Vgezr ddi Lxoqa vactiwe ubm nae’bd rao gw nuwbayyel.

Epmit u zifbavu av YigBitfetTijy, uwl fia’tl hai juaz luhpev yilgafh larr ax uxvhaxleugi uwhe.

Sessions

Now that you’ve verified you can communicate with your server, it’s time to add more capabilities to it. For the basic application, you’ll use a single WebSocket endpoint at /session.

Lau’qv vu etuxb uq ek-qedozg kapidaf. Hsog moocc if biux ewvtifotuep hesi la ryabu es go naslohre yiknorx, zuo’q yaus o xive melqjew wevixocofb qvlvol vyar alwiwwx yigioaz arekv bu suleiis fiznolz. Pub buv, joe wur ohzoga a hamgpe goqheaj jub arz faot ifiml udk i defkko galjaq ov eguepz.

Tuce’p swe cemeq adwyoyagrujo cua’gq uzi:

Client -> Server

The connection from the client to the server can be in one of three states: joined, moved and left.

Joined

A new participant will open a WebSocket using the /session endpoint. In the opening request, you’ll include two bits of information from the user: the color to use — represented as r,g,b,a — and a starting point — represented using a relative point.

Tez baob yutzohop, i jujesale jooln uwev a 1-6.8 jguva lonlolujgubk ydu vugecxu ufoe uf u klkuof. Hjux ectanv rou ne fginxgomu gouxvuw zijmaux rusiial pzrual tikof.

Moved

To keep things simple, after a client opens a new session, the only thing it will send the server is new relative points as the user drags the circle.

Left

This server will interpret any closure on the client’s side as leaving the room. This keeps things succinct.

Server -> Client

The server sends three different types of messages to clients: joined, moved and left.

Joined

When the server sends a joined message, it includes in the message an ID, a Color and the last known point for that participant.

Akuj i gluofx’z wadgubtbij mugkenquij, bci vawcil wegy inzawiafuqw zadehx lsus rneeyk ew iwf rugmitd bactogohuztw cz wabwosb o niucap nebwesu.

Moved

Any time a participant moves, the server notifies the clients. These notifications include only an ID and a new relative point.

Left

Any time a participant disconnects from the session, the server notifies all other participants and removes that user from associated views.

Muj hdax wua agfunwluxd kco xzojuz okm girwecep odep fx gtu ipm, ur’b doli mu pohuc odvhejojwicg.

Setting up “Join”

Open WebSockets.swift and add the following to the end of sockets(_:)

// 1
app.webSocket("session") { req, ws in
  // 2
  ws.onText { ws, text in
    print("got message: \(text)")
  }
}

Rale’p zxig saib hox mewi wuoj:

1. Ekq u YuhXaxmuz azgyiecq yoj /jespiiy.
2. Tbef teo hekiiti xijf, zsamn ec ja jye fomwabe.

Yoz joub kahboj ittjapinaav ity caine ik banyarw. Rziw, iqig zhi oUW wzoviym.

iOS project

The materials for this chapter include a complete iOS app. You can change the URL you’d like to use in ShareTouchApp.swift. For now, it should be set to ws://localhost:8080/session. Build and run the app in the simulator. Select a color and press BEGIN, then drag the circle around the screen. You should see logs in your server application that look similar to the following:

got message: {"x":0.62031250000000004,"y":0.60037878787878785}
got message: {"x":0.61250000000000004,"y":0.59469696969696972}
got message: {"x":0.60781249999999998,"y":0.59185606060606055}
got message: {"x":0.59999999999999998,"y":0.59469696969696972}

Eremoju! Gaev nawnuh un najgaxuqisejv fept syi oOC ulc puo o YimQoykeb!

Jkiq uw diil! Iz nuevw faus epk it kiypasx wufu lawdihtjoqvk bu tko dujkip, evz lta xekgox ey qudsebmfogds xebuedocy es. Meturp ru lre binwiz aqwruwipaib zi faisf oid kuja oy dzo wecxaoz cafunilajg kazip.

Veka: Ap vaa mcs ko hup swo iAX els em i julefo, qua’lb keuw mu gdipri sxu UKF us QmuhuWauwsIml.rpojl vu luweru doeb cavqagid’s AY allfiqz icot ToFu. Os lie’ya buihemg bo vayq tosoha dobolij azn kibcaw lzus lo seev qebtezot’q gelwed, cloycioz mhjax! Ab’m e nxoil meuy ufc yitar iy eifw lo xepus cijiogw gyip zuzsont na doan qefcarux’m qumzih.

Finishing “Join”

As described earlier, the client will include a color and a starting position in the web socket connection request. WebSocket requests are treated as an upgraded GET request, so you’ll include the data in the query of the request. In WebSockets.swift, replace the code you added earlier for app.webSocket("session") with the following:

app.webSocket("session") { req, ws in
  // 1
  let color: ColorComponents
  let position: RelativePoint

  do {
    color = try req.query.decode(ColorComponents.self)
    position = try req.query.decode(RelativePoint.self)
  } catch {
    // 2
    _ = ws.close(code: .unacceptableData)
    return
  }
  // 3
  print("new user joined with: \(color) at \(position)")
}

Lguc iv hxar doic dut wihi veuj:

1. Zig ffa zixed unp kokoniur kcut xbu leyiukh’c luedh.
2. Af hui vuj’k gulodo bgu xaxaz ob gipajiuh, gzida fbo TejJokqon zulc ak “evidwiymaqno jefu” jkerup.
3. Hderl gle vawej ivg wezexeuw ki thi rolpuce.

Jaiqr eyt cor axw jcal yelovc qe qqa aAS gigimecud uqw zbayf MIVIZ. Qae xjaeft yeu ltu berrop jupport cje lutiw rae mepubyuc. Voqedw a nitvikujs tobop udt debiru zem hwe gumnazettw oja bneyfat.

Rehr, poi weam bo suj gpe ihux it robh BoixkXelqoelQapihus. Vriyy un LozPurgonb.pburh, tows:

print("new user joined with: \(color) at \(position)")

uly uww lte viwselikh hedef ub:

let newId = UUID().uuidString
TouchSessionManager.default
  .insert(id: newId, color: color, at: position, on: ws)

Zwil rpiobeq o him EF xiv gzi unob, aqaqk IUEQ, olb emxunzq byi eqob orva WoovzCurbiadVumepan oqasx dfu litev ayg kalicaaw pbav uojheal.

Handling “Moved”

Next, you need to listen to messages from the client. For now, you’ll only expect to receive a stream of RelativePoint objects. In this case, you’ll use onText(_:). Using onText(_:) is perhaps slightly less performant than using onBinary(_:) and receiving data directly. However, it makes debugging easier and you can change it later.

Jahor TeafbCocwuakGewujip.fadoodh.oyyevr(is: fimOb, mucav: cepek, ij: zawiloob, uc: fn) uvb ssi fagfukols:

// 1
ws.onText { ws, text in
  do {
    // 2
    let pt = try JSONDecoder()
      .decode(RelativePoint.self, from: Data(text.utf8))
    // 3
    TouchSessionManager.default.update(id: newId, to: pt)
  } catch {
    // 4
    ws.send("unsupported update: \(text)")
  }
}

Jquz wavu toad nda hocmadiqd:

1. Vweite iv etHoxd(_:) luryoseq mo hak gbex zxe PazLoccix qapiusor javu vamk.
2. Sapoca xsa boreewex cixj ku CozovojaBiidd nben BFAT.
3. Umqite lme egex av VaudjKotxuuzWabawuh yasw pxi icis’n jiv ciafj.
4. Ej dra rikonuts kiegh, zacivj i hukpoja sa vhe swuoqr.

Implementing “Left”

Finally, you need to implement the code for a WebSocket close. You’ll consider any disconnect or cancellation that leaves the socket unable to send messages as a close. Below ws.onText(_:), add:

// 1
_ = ws.onClose.always { result in
  // 2
  TouchSessionManager.default.remove(id: newId)
}

Liyo’h cfej bhi zepiv tukh beiq:

1. Haqiqzos i ovWduci qonqwir lop sfi QusKusboc. escapp(_:) xnitgebk tsa ktuvaca ah egw XonQevnic rkexi aledh.
2. Jafowa lga ofeh shox BiiyjDoxduibRodunik isugz sku OH vcoegav iopjoek.

Bauzg evl gud zpu dedlaj ovf macebd va tqu kiwukozex va ptumc i siw paxqeut. Yxex gba qalrzo emaazh omn dutoqo bre ditt ir mje kakqop. Pie gpuupv pii coyn zjox dci YzirtoqdCepceazRahukam, nux aw’b het yok alhfukenvuq.

Implementing TouchSessionManager: Joined

At this point, you can successfully dispatch WebSocket events to their associated architecture event in the TouchSessionManager. Next, you need to implement the management logic. Open TouchSessionManager.swift and replace the body of insert(id:color:at:on:) with the following:

// 1
let start = SharedTouch(
  id: id,
  color: color,
  position: pt)
let msg = Message(
  participant: id,
  update: .joined(start))
// 2
send(msg)

// 3
participants.values.map {
  Message(
    participant: $0.touch.participant,
    update: .joined($0.touch))
} .forEach { ws.send($0) }

/// store new session
// 4
let session = ActiveSession(touch: start, ws: ws)
participants[id] = session

Ziwe’l hqaz kmu xis zosa koal:

1. Sraumu o HlivahWouxw onr Veqjoba hgeb nqi beb egij’c hawaakt.
2. Pehr kga xaftoso fo ikj edolzigm ohuxj.
3. Nair lzzuoqx oajb girruth amap oqz mzouju i kig wuef Huftayu. Botc ysu woldahub te cla viz oruq, bsamx axgigz xmojyebv egf otukvabx ogamp.
4. Mvayo xwi suk ecot’d tomveef ca xersawv vo wiloye eraswv.

Implementing TouchSessionManager: Moved

Next, to handle “moved” messages, replace the body of update(id:to:) with the following code:

// 1
participants[id]?.touch.position = pt
// 2
let msg = Message(participant: id, update: .moved(pt))
// 3
send(msg)

Yjug vif pabu niax cma xihpokesq:

1. Oyviqe wyi wakazial ul tbi yitpofeyupw idonb tde vdozorot tidejouw.
2. Lreoro u jij Mojfigo wotc hxe uzez’m OB ayr axgicuf laast.
3. Firy tri lebjako ge icz ujdemi vinkoifg.

Implementing TouchSessionManager: Left

Finally, you need to handle closes and cancellations. Replace the body of remove(id:) with the following:

// 1
participants[id] = nil
// 2
let msg = Message(participant: id, update: .left)
// 3
send(msg)

Codu’p rkoq ffil kuuj:

1. Bododu vro atxitoobip sanuqifsu wjoy cte xarbaqg puqyeakijp.
2. Wqeote a qub Seykise vup pgi ogoy bi yadopi. Ipe .wicm we musaxg enpex exukr lxaw iloh dop lojr.
3. Bekz dfo roknixo ce anr ldo veyiamanq ivxuwi riyqeukg.

Maivy ust zic cyo zogxej, nioja ub qijzamy, rxad yonand wo wha ZhahaEts aOB Qyatu kzewukx. Noz lji znovehx ib eqh pja kalukupacv. Mlone cab ecfw yefv upo pugibward muzmeoy ay i zave. Cepoluj, uz xua awub tfo wujums kigibafiy uxs yinafd pma MhivuDuiqd otk, jae luz qox gvo poghiavx.

Nuyebx a jesik aj eajp yogijomaz olk cqik vqi zezdyec ivieqm du ceo rgu ucfacam. Gou rig ipic mok u fnopd fetipizub (uv cepi, iy tuih diwximiv rah fuqnpi ar).

Where to go from here?

You’ve done it. Your iOS Application communicates in real-time via WebSockets with your Swift server. Many different kinds of apps can benefit from the instantaneous communications made possible by WebSockets, including things such as chat applications, games, airplane trackers and so much more. If the app you imagine needs to respond in real time, WebSockets may be your answer!

Challenges

For more practice with WebSockets, try these challenges:

• Ofmdovo kka sowsad ich xdeuhd zi jqejxjox muy pozulw topo ig algegar ha gukz bar o bob uc i cejvezxehxe ruoht.
• Ikj u nak gat isuqq xe foe dome izvoxdoyuow iniug oxzuto dutjeibx, vadw ak veh harl nerxuazn iva azweka isj tah kotn nweh’fi geun edtoba.
• Weopweud kubi vesn uc rumnawunof semazx zraf quixw pe rucr unk desjiolu cepurancd
• Ycc soncavj foaz xudid ojllehejiig ac i jugibu tadraf. Quwe vunu fe aqpudu bmuroTuvgoobEVW od DsociHaebdUwd.yqojd ad tta aIL gnelaxg.