impl client/server version handshake

client/src/Connection.ts

@@ -2,11 +2,15 @@ import {
   C2SRequestType,
   C2SRequestTypes,
   C2SWSOpenPayload,
+  C2S_HELLO,
   HTTPRequestPayload,
   HTTPResponsePayload,
+  PROTOCOL_VERSION,
   ProtoBareHeaders,
   S2CRequestType,
   S2CRequestTypes,
+  S2C_HELLO_ERR,
+  S2C_HELLO_OK,
   Transport,
   WSClosePayload,
   WSErrorPayload,
@@ -33,6 +37,7 @@ type OpenWSMeta = {
 };
 
 export class Connection {
+  initialized = false;
   requestCallbacks: Record<number, Function> = {};
   openRequestStreams: Record<number, ReadableStreamDefaultController<any>> = {};
   openingSockets: Record<number, OpenWSMeta> = {};
@@ -40,8 +45,37 @@ export class Connection {
 
   counter: number = 0;
 
+  static uninitializedError() {
+    throw new Error("Connection not initialized");
+  }
+
   constructor(public transport: Transport) {
-    transport.ondata = this.ondata.bind(this);
+    transport.ondata = Connection.uninitializedError;
+  }
+
+  async initialize(): Promise<void> {
+    const onDataPromise = (): Promise<ArrayBuffer> => {
+      return new Promise((res) => {
+        this.transport.ondata = res;
+      });
+    };
+    // maybe some sort of timeout here?
+    // this code is not the best tbh
+    this.transport.send(new TextEncoder().encode(C2S_HELLO + PROTOCOL_VERSION));
+    const msg = await onDataPromise();
+    const msgText = new TextDecoder().decode(msg);
+    if (msgText === S2C_HELLO_OK) {
+      this.transport.ondata = this.ondata.bind(this);
+      this.initialized = true;
+    } else if (msgText.startsWith(S2C_HELLO_ERR)) {
+      const expectedVersion = msgText.slice(S2C_HELLO_ERR.length);
+      throw new Error(
+        `We are running protocol version ${PROTOCOL_VERSION}, ` +
+          `but server expected ${expectedVersion}`
+      );
+    } else {
+      throw new Error("Unexpected server hello response");
+    }
   }
 
   nextSeq() {
@@ -49,6 +83,8 @@ export class Connection {
   }
 
   ondata(data: ArrayBuffer) {
+    if (!this.initialized) return;
+
     let cursor = 0;
     const view = new DataView(data);
 
@@ -148,6 +184,10 @@ export class Connection {
     type: C2SRequestType,
     data?: ArrayBuffer | Blob
   ): Promise<void> {
+    if (!this.initialized) {
+      Connection.uninitializedError();
+    }
+
     let header = new window.ArrayBuffer(2 + 1);
     let view = new DataView(header);
 
@@ -174,6 +214,10 @@ export class Connection {
     },
     body: ReadableStream<ArrayBuffer | Uint8Array> | null
   ): Promise<{ payload: HTTPResponsePayload; body: ArrayBuffer }> {
+    if (!this.initialized) {
+      Connection.uninitializedError();
+    }
+
     const payload: HTTPRequestPayload = { ...data, hasBody: Boolean(body) };
     let json = JSON.stringify(payload);
 
@@ -202,11 +246,15 @@ export class Connection {
     onclose: (code: number, reason: string, wasClean: boolean) => void,
     onmessage: (data: any) => void,
     onerror: (message: string) => void,
-    arrayBufferImpl: ArrayBufferConstructor,
+    arrayBufferImpl: ArrayBufferConstructor
   ): {
     send: (data: any) => void;
     close: (code?: number, reason?: string) => void;
   } {
+    if (!this.initialized) {
+      Connection.uninitializedError();
+    }
+
     const payload: C2SWSOpenPayload = { url: url.toString(), protocols };
     const payloadJSON = JSON.stringify(payload);
     let seq = this.nextSeq();

client/src/DevWsTransport.ts

@@ -24,4 +24,8 @@ export class DevWsTransport extends Transport {
   send(data: ArrayBuffer) {
     this.ws.send(data);
   }
+
+  close() {
+    this.ws.close();
+  }
 }

client/src/RTCTransport.ts

@@ -8,11 +8,9 @@ const rtcConf = {
   ],
 };
 
-
 export type Offer = { offer: any; localCandidates: any };
 export type Answer = { answer: any; candidates: any };
 
-
 export class RTCTransport extends Transport {
   peer: RTCPeerConnection;
 
@@ -57,6 +55,10 @@ export class RTCTransport extends Transport {
     this.dataChannel.send(data);
   }
 
+  close() {
+    this.dataChannel.close();
+  }
+
   async createOffer(): Promise<Promise<Offer>> {
     const localCandidates: RTCIceCandidate[] = [];
 

frontend/src/App.svelte

@@ -52,10 +52,12 @@
 
   let showTrackerList = false;
 
-  function onTransportOpen() {
+  async function onTransportOpen() {
     console.log("Transport opened");
 
     let connection = new Connection(transport);
+    // TODO: error handling here
+    await connection.initialize();
     let bare = new AdriftBareClient(connection);
     console.log(setBareClientImplementation);
     setBareClientImplementation(bare);

protocol/src/Transport.ts

@@ -3,4 +3,5 @@ export abstract class Transport {
   constructor(public onopen: () => void, public onclose: () => void) {}
 
   abstract send(data: ArrayBuffer): void;
+  abstract close(): void;
 }

protocol/src/index.ts

@@ -55,4 +55,11 @@ export type WSErrorPayload = {
 // WebRTC max is 16K, let's say 12K to be safe
 export const MAX_CHUNK_SIZE = 12 * 1024;
 
+export const S2C_HELLO_OK = ":3";
+// these two end with a version string
+export const C2S_HELLO = "haiii ";
+export const S2C_HELLO_ERR = ":< ";
+
+export const PROTOCOL_VERSION = "1.0";
+
 export { Transport } from "./Transport";

server/src/dev.ts

@@ -31,7 +31,10 @@ app.post("/connect", (req, res) => {
 
 app.ws("/dev-ws", (ws, _req) => {
   console.log("ws connect");
-  const client = new AdriftServer((msg) => ws.send(msg));
+  const client = new AdriftServer(
+    (msg) => ws.send(msg),
+    () => ws.close()
+  );
 
   ws.on("message", (msg) => {
     if (typeof msg === "string") {

server/src/rtc.ts

@@ -75,9 +75,12 @@ export async function answerRtc(data: any, onrespond: (answer: any) => void) {
 
     dataChannel.onopen = () => {
       console.log("opened");
-      server = new AdriftServer((msg) => {
-        if (dataChannel.readyState === "open") dataChannel.send(msg);
-      });
+      server = new AdriftServer(
+        (msg) => {
+          if (dataChannel.readyState === "open") dataChannel.send(msg);
+        },
+        () => dataChannel.close()
+      );
     };
     dataChannel.onclose = () => {
       console.log("closed");

server/src/server.ts

@@ -3,12 +3,16 @@ import { IncomingMessage, STATUS_CODES } from "http";
 import { WebSocket } from "isomorphic-ws";
 import {
   C2SRequestTypes,
+  C2S_HELLO,
   HTTPRequestPayload,
   HTTPResponsePayload,
   MAX_CHUNK_SIZE,
+  PROTOCOL_VERSION,
   ProtoBareHeaders,
   S2CRequestType,
   S2CRequestTypes,
+  S2C_HELLO_ERR,
+  S2C_HELLO_OK,
   WSClosePayload,
   WSErrorPayload,
 } from "protocol";
@@ -32,16 +36,41 @@ function bareErrorToResponse(e: BareError): {
 }
 
 export class AdriftServer {
+  initialized: boolean = false;
   send: (msg: ArrayBuffer) => void;
+  close: () => void;
   requestStreams: Record<number, Promise<Writable>> = {};
   sockets: Record<number, WebSocket> = {};
   events: EventEmitter;
 
-  constructor(send: (msg: ArrayBuffer) => void) {
+  constructor(send: (msg: ArrayBuffer) => void, close: () => void) {
     this.send = send;
+    this.close = close;
     this.events = new EventEmitter();
   }
 
+  handleHello(msg: ArrayBuffer) {
+    try {
+      const text = new TextDecoder().decode(msg);
+      if (!text.startsWith(C2S_HELLO)) {
+        this.close();
+        return;
+      }
+      // later if we want we can supported multiple versions and run different behavior based
+      //  on which we are talking to, might be too much effort idk
+      const version = text.slice(C2S_HELLO.length);
+      if (version === PROTOCOL_VERSION) {
+        this.send(new TextEncoder().encode(S2C_HELLO_OK));
+        this.initialized = true;
+      } else {
+        this.send(new TextEncoder().encode(S2C_HELLO_ERR + PROTOCOL_VERSION));
+        this.close();
+      }
+    } catch (_) {
+      this.close();
+    }
+  }
+
   static parseMsgInit(
     msg: ArrayBuffer
   ): { cursor: number; seq: number; op: number } | undefined {
@@ -207,6 +236,11 @@ export class AdriftServer {
   }
 
   async onMsg(msg: ArrayBuffer) {
+    if (!this.initialized) {
+      this.handleHello(msg);
+      return;
+    }
+
     const init = AdriftServer.parseMsgInit(msg);
     if (!init) return;
     const { cursor, seq, op } = init;