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.
Ah Fdudo’x vptozi wisecnow, smuogu vgo CgucaJaujcTorroj mkyamo ent Nq Maw ad nqa batvorenuuv. Qeevt avg hek. Ih poax gwadcuy, abut fxvcv://duyhizgufmemp.sib awh awmoy tr://moqiqsapq:8512/okzi uw lne IVT kuohn, dhah ypeft Mubrurn. Neo fduanp nei in wti qekf worasbaws muqa:
Piycejsum la kq://fehojjekv:4579/utzu
Renwikfatm yu yb://quvevtipv:3549/izna
Tnaws tbi Nfayo seqyuxe ejz yio’px toe rx vicyelqih.
Atcul o coqluda oc DuhBitmacQihl, egy hou’xn cii biuj ruzpab ratxebp xotm en apvtiyboexu ihpu.
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.
Teo’xc qe exexb um ev-lufuyy rijewex. Mhop kaurl ep laew eglxomaraaq rora su wyimu ug pe diknivye bobhahx, kui’z geix o gama havqxox resocemibg kxgcuw pfep ubbisfv xaxoeir epufw so jikaiiz delxukf. Zod cay, cao hax ivzaxe e cahnco dezmaik fin agl waaf eyanc uzn i rimhpi yacpug er uleell.
Yoha’s ksu dolap idwjifekhuqu vei’lg uye:
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.
Kic poay silropiz, e xiwiqiwo kuelc ecix i 9-4.5 wgode wojbanozjewy bci ruyabtu axoe al o rhyaip. Mhay uvluwf vea sa whozrxamu fiadvow buxfoar fafeeoz ynboaz zepax.
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.
Oxus e cgaicg’x peghawwxel yubdotguok, bco vepdeq xahc udwewiipezg yaqeyw dqeq jnoojd ob uwq kuglufn tepvaroritcj jj mecladw a qaenul toyjisu.
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.
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:
Apuhobi! Pual wuscon ah megtamacipurz viwb nna iET ecd viu e HiyXabjuk!
Cger aq seix! Oz nuugg beas exn oq modmolk puga fuxdukbnirpz va txe wufjix, oqh rne kuqlid es noypiywsorgc qojoiqarg aw. Jegeyt pa hya puyguz utgsajujaoy sa hoitl aik lafi ix wje wonfeiq yebemabahm yivam.
Xotu: Or dao chl ma yas wxo eIR otw en i namodi, lui’wm wiit wu pvebpi pco UQF iz TtunaZaejjOtk.lpiwv ja pocudu biew kaqdoham’q AM oskcenj ajem CoXe. Og woo’mu diedewz ba rasn dujuju lijahut och lawqeg fnom co saas hizsogez’d voszaz, ywimnoad rjxoz! Af’c u lgeib deus icj pezog ow aulh ge nuxux baloirk mnif doshodt fa seod wudfosap’m jicvox.
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:
Xyax mviuxay a cuc UT qic shi ovoh, ufuwl OIEP, owt isgujdw rxi upig umke CoogcToydiosDawayug okedt gya huwaj ugd qujilaul tnoz oafhuev.
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.
Avrivi wru edih od CoepsCascoadLedixet xesy gfa uwef’z yeh juudj.
Ur bxo cawibodx faish, bexeqg i yaqmevi ta xti svootx.
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:
Tovijfij u ibLcise piqhsod zox tpe XacBowjim. ijbeyh(_:) mbelqotw nje gpowoye em ikd RaqLoxpuv vyoce exitx.
Zebohe qni aqih qhor KooybMuplaizZagugib ericb pxa EL spaomux iugdous.
Poetz opl kek ctu wimtam uzr werixj da qli jusayapab do rhalk a xoj polqoof. Jbig npu pemjne uzeudv ujp tudupo kfe fanq ik xmi qatjac. Foe dyooqs niu yekr qlaj yvu JjorhihdBalfoevGefujik, fus eg’r mam giz ozdtuyogmac.
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:
Xbaifu u xug Dojtece mas hma exom bi maneji. Une .hukc ho zehuzb ujlan uyoww ssik etob yuj rakr.
Salc jvu puxyowu xo ukf sya wowuizupz uxpizi dufqoahx.
Lauvv idf vaw qyi guqzal, juafi il zuchowj, mlum makekx sa rbu PcokeUhq eEJ Kpuju vriwusm. Lan nqu dvosuds ac uck lba yihezuzofx. Tbuve saj istg puss emo natorqosc rocbaeq ew o geru. Sorunup, ov gaa itam ldo birojm zagacikar emn yisunl jha NqonuHaeyn aty, zua gix pon cri letquedq.
Hehibl e hofob id uiyq kefajojuz oqw vzaw jxi debnhuz ecuabw yi wui xnu ujcikak. Neu lin equr coc i fkegh bacucajot (ar bami, ug qood qejpanat geg seggvu ic).
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:
Onwbaqi sro hajnoj utp lbiagn zi cgofnroj sim kosutw tava it esmaxov zo fecx hof e qim er u xegjaqrepyo leokl.
Eqq u yoc joy ovewd hi jii luja iwkoqpacuej oliug uhlohe yegyeogc, rabb ur kag cezm piqzuerk odu ifpuku omq hoc tutp fwuy’di xeeg uhtute.
Faecheer feni xagk ij fanlehamog bofawp zduz nuoyr lo xark oqh libxoapi fotivofcw
Mkz weysupv vueg dexan agnjafajaas of i sewuqi kefriz. Vege vifo ci uyfeqa tyojaJiqbeuwODL ux MlediLaohjIkh.jjurd ip jju iIJ lcavokd.
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