From a53cd1b7717144d27a31c4e3cd8c93da2b5bc7b1 Mon Sep 17 00:00:00 2001
From: hippoz <paperplanelive@gmail.com>
Date: Wed, 3 Feb 2021 02:18:28 +0200
Subject: [PATCH] proof-of-concept sending packets to client

---
 example/example.js |  1 +
 lib/Parser.js      | 34 +++++++++++++++++++++++++++++++---
 lib/Socket.js      | 21 +++++++++++++++++++++
 3 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/example/example.js b/example/example.js
index 8cc6810..ce4af09 100644
--- a/example/example.js
+++ b/example/example.js
@@ -8,6 +8,7 @@ const wormhole = new Wormhole({ urls: [ '/hello' ], httpServer });
 
 wormhole.on('connect', ({ socket, accept, reject }) => {
     accept();
+    socket.sendText('hello');
 });
 
 httpServer.listen(8080);
\ No newline at end of file
diff --git a/lib/Parser.js b/lib/Parser.js
index 6a7ed20..43da7a4 100644
--- a/lib/Parser.js
+++ b/lib/Parser.js
@@ -14,6 +14,8 @@ class WebsocketFrame {
         this.MASK = undefined;
         this.PayloadLen = undefined;
 
+        this.PayloadLenEx = undefined; // This is for when PayloadLen needs to be extended
+
         // 4 bytes - masking key
         this.MaskingKey = undefined;
 
@@ -23,6 +25,30 @@ class WebsocketFrame {
     }
 }
 
+WebsocketFrame.prototype.toBuffer = function() {
+    const packet = [];
+
+    const firstByte = this.FIN << 0x07 | this.RSVx << 0x06 | this.Opcode;
+    const secondByte = this.MASK << 0x07 | this.PayloadLen;
+    const headerBuffer = Buffer.from([firstByte, secondByte]);
+    packet.push(headerBuffer);
+
+    let lenBuffer;
+    if (this.PayloadLen === 126) {
+        lenBuffer = Buffer.alloc(2);
+        buf.writeUint16BE(this.PayloadLenEx);
+    } else if (this.PayloadLen === 127) {
+        lenBuffer = Buffer.alloc(8);
+        buf.writeBigUint64BE(this.PayloadLenEx);
+    }
+    lenBuffer && packet.push(lenBuffer);
+
+    this.MASK && packet.push(this.MaskingKey);
+    packet.push(this.PayloadData);
+
+    return Buffer.concat(packet);
+};
+
 const parseWebsocketFrame = (data) => {
     const firstByte = data.getUint8(0);
     const secondByte = data.getUint8(1);
@@ -42,18 +68,20 @@ const parseWebsocketFrame = (data) => {
 
     // Handle Payload len cases and set the masking key offset
     if (frame.PayloadLen === 126) {
-        frame.PayloadLen = data.getUint16(2);
+        frame.PayloadLenEx = data.getUint16(2);
         maskingKeyOffset = 4; // 4 byte offset, because we also read 2 bytes with getUint16 above (2 bytes (normal size) + 2 bytes)
     } else if (frame.PayloadLen === 127) {
-        frame.PayloadLen = data.getBigUint64(2);
+        frame.PayloadLenEx = data.getBigUint64(2);
         maskingKeyOffset = 10; // 10 byte offset, because we also read 8 bytes with getBigUint64 above (2 bytes (normal size) + 8 bytes)
+    } else {
+        frame.PayloadLenEx = frame.PayloadLen;
     }
     
     const maskingKeyEnd = maskingKeyOffset + 4; // (4 bytes because it is a 32 bit value)
     if (frame.MASK) frame.MaskingKey = data.buffer.slice(maskingKeyOffset, maskingKeyEnd); // Create a new buffer starting at the masking key offset and ending at the masking key end (duh).
 
     // TODO: Separate extension data from application data
-    frame.PayloadData = data.buffer.slice(maskingKeyEnd, maskingKeyEnd + frame.PayloadLen); // Create a new buffer that starts at the end of the masking key and ends at (the end of the masking key + payload length)
+    frame.PayloadData = data.buffer.slice(maskingKeyEnd, maskingKeyEnd + frame.PayloadLenEx); // Create a new buffer that starts at the end of the masking key and ends at (the end of the masking key + payload length)
 
     // TODO: implement unmasked string decoding
     if (frame.MASK) {
diff --git a/lib/Socket.js b/lib/Socket.js
index c51f080..0bd1c49 100644
--- a/lib/Socket.js
+++ b/lib/Socket.js
@@ -16,6 +16,27 @@ class Socket {
     }
 }
 
+Socket.prototype.sendText = function(text) {
+    const frame = new parser.WebsocketFrame();
+    frame.FIN = 1;
+    frame.RSVx = 0;
+    frame.Opcode = 0x01;
+
+    frame.MASK = 0;
+    const length = text.length;
+    if (length > 125) {
+        frame.PayloadLen = 126;
+    } else if (length >= 65536) {
+        frame.PayloadLen = 127;
+    } else if (length <= 125) {
+        frame.PayloadLen = length;
+    }
+    frame.PayloadLenEx = length;
+    frame.PayloadData = Buffer.from(text);
+
+    this._socket.write(frame.toBuffer());
+};
+
 Socket.prototype._decodePayload = function(payload) {
     console.log(parser.parseWebsocketFrame(new DataView(payload)));
 };