diff --git a/web/app.js b/web/app.js
index 47f683f..3026fa2 100644
--- a/web/app.js
+++ b/web/app.js
@@ -1,69 +1,9 @@
+/**
+ * If this character is included in the received data chunk,
+ * it means that transfer completed.
+ */
 var EOT = '\u0004';
 
-class SerialPortHandler {
-  constructor(options, onConnect, onDisconnect) {
-    this.encoder = new TextEncoder();
-    this.decoder = new TextDecoder();
-    this.onConnect = onConnect;
-    this.onDisconnect = onDisconnect;
-    this.options = options;
-    this.port = null;
-    this.isOpened = false;
-    this.#setupListeners();
-  }
-
-  async open() {
-    try {
-      const port = await navigator.serial.requestPort();
-      await port.open(this.options);
-
-      this.port = port;
-      this.isOpened = true;
-
-      return this.port.getInfo();
-    } catch (error) {
-      console.error(error);
-      throw error;
-    }
-  }
-
-  async close() {
-    await this.port.close();
-    this.isOpened = false;
-  }
-
-  async write(data) {
-    const writer = this.port.writable.getWriter();
-    const encoded = this.encoder.encode(data);
-    await writer.write(encoded);
-    writer.releaseLock();
-  }
-
-  async read() {
-    const reader = this.port.readable.getReader();
-    let chunks = '';
-    while (true) {
-      const { value, done } = await reader.read();
-      const decoded = this.decoder.decode(value);
-
-      chunks += decoded;
-
-      if (done || decoded.includes('\u0004')) {
-        console.log('Reading done.');
-        reader.releaseLock();
-        break;
-      }
-    }
-
-    return chunks;
-  }
-
-  #setupListeners() {
-    navigator.serial.addEventListener('connect', this.onConnect);
-    navigator.serial.addEventListener('disconnect', this.onDisconnected);
-  }
-}
-
 class Application {
   constructor(root) {
     if (!('serial' in navigator)) {
@@ -148,4 +88,68 @@ class Application {
   }
 }
 
+class SerialPortHandler {
+  constructor(options, onConnect, onDisconnect) {
+    this.encoder = new TextEncoder();
+    this.decoder = new TextDecoder();
+    this.onConnect = onConnect;
+    this.onDisconnect = onDisconnect;
+    this.options = options;
+    this.port = null;
+    this.isOpened = false;
+    this.#setupListeners();
+  }
+
+  async open() {
+    try {
+      const port = await navigator.serial.requestPort();
+      await port.open(this.options);
+
+      this.port = port;
+      this.isOpened = true;
+
+      return this.port.getInfo();
+    } catch (error) {
+      console.error(error);
+      throw error;
+    }
+  }
+
+  async close() {
+    await this.port.close();
+    this.isOpened = false;
+  }
+
+  async write(data) {
+    const writer = this.port.writable.getWriter();
+    const encoded = this.encoder.encode(data);
+    await writer.write(encoded);
+    writer.releaseLock();
+  }
+
+  async read() {
+    const reader = this.port.readable.getReader();
+    let chunks = '';
+    while (true) {
+      const { value, done } = await reader.read();
+      const decoded = this.decoder.decode(value);
+
+      chunks += decoded;
+
+      if (done || decoded.includes('\u0004')) {
+        console.log('Reading done.');
+        reader.releaseLock();
+        break;
+      }
+    }
+
+    return chunks;
+  }
+
+  #setupListeners() {
+    navigator.serial.addEventListener('connect', this.onConnect);
+    navigator.serial.addEventListener('disconnect', this.onDisconnected);
+  }
+}
+
 new Application(document.getElementById('app'));