WebSockets & Realtime Systems Programming · درس

دورة حياة الاتصال وحالاته

استكشفوا الحالات المختلفة لاتصال WebSocket، من الفتح إلى الإغلاق، وكيفية إدارتها.

دورة حياة الاتصال وحالاته درس مجاني في WebSockets & Realtime Systems Programming على CoddyKit. هذا هو الدرس 3 من أصل 4. يمكنك قراءة الدرس كاملاً أدناه مجاناً — ثم تمرن عليه مباشرة في المتصفح باستخدام محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7. هذا الدرس جزء من مسار التعلم في WebSockets & Realtime Systems Programming، وتقدمك يتزامن عبر الويب وتطبيق CoddyKit. تتضمن دورة WebSockets & Realtime Systems Programming 4 دروس في المجموع.

بعض أجزاء هذا الدرس لم تُترجم بعد وتظهر باللغة الإنجليزية.

Understanding Connection States

When you work with WebSockets, it's crucial to know the current state of your connection. This helps you manage data flow and handle disconnections gracefully.

Just like a phone call goes through phases (dialing, connected, hanging up), a WebSocket connection has a defined lifecycle with specific states.

The CONNECTING State (0)

The very first state of a WebSocket is CONNECTING. This happens immediately after you create a new WebSocket object.

Its numeric value is 0.
In this state, the client is trying to establish a connection with the server.
This includes the initial HTTP handshake process that upgrades the connection to WebSocket.
You cannot send messages yet.

Connecting with Node.js

When a WebSocket client attempts to connect, it enters the CONNECTING state (readyState = 0). This is where the initial handshake occurs.

To run this Node.js example:

Make sure you have Node.js installed.
Open your terminal and run npm init -y
Install the ws library: npm install ws
Save the code below as index.js.
Run node index.js.

Note: You'll need a WebSocket server running on ws://localhost:8080 for a successful connection.

const WebSocket = require('ws');

const ws = new WebSocket('ws://localhost:8080');

console.log(`Initial state: ${ws.readyState}`); // Expected: 0 (CONNECTING)

ws.onopen = () => {
  console.log(`Connection opened! State: ${ws.readyState}`); // Expected: 1 (OPEN)
  ws.send('Hello from CoddyKit client!');
  setTimeout(() => ws.close(1000, 'Demo complete'), 2000);
};

ws.onmessage = (event) => {
  console.log(`Received: ${event.data}`);
};

ws.onclose = (event) => {
  console.log(`Connection closed. Code: ${event.code}, Reason: ${event.reason}`);
  console.log(`Final state: ${ws.readyState}`); // Expected: 3 (CLOSED)
};

ws.onerror = (error) => {
  console.error('WebSocket Error:', error.message);
};

The OPEN State (1)

Once the handshake is complete and the connection is successfully established, the WebSocket enters the OPEN state.

Its numeric value is 1.
In this state, the connection is ready for bidirectional communication.
You can send data to the server, and the server can send data to you.
This is the active communication phase.

Handling the OPEN Event

The onopen event is fired once the WebSocket connection transitions from CONNECTING to OPEN. This is your cue that you can start sending messages.

Run this Node.js example to see the onopen event in action:

const WebSocket = require('ws');
const ws = new WebSocket('ws://localhost:8080');

ws.onopen = () => {
  console.log('WebSocket connection is now OPEN!');
  console.log(`Current state: ${ws.readyState}`); // Expected: 1 (OPEN)
  ws.send('Ready to chat!');
  setTimeout(() => ws.close(), 1500); // Close after a short delay
};

ws.onmessage = (event) => {
  console.log('Received:', event.data);
};

ws.onclose = () => {
  console.log('Connection closed.');
};

ws.onerror = (error) => {
  console.error('Error:', error.message);
};

The CLOSING State (2)

When either the client or the server decides to terminate the connection, it enters the CLOSING state.

Its numeric value is 2.
This state occurs after ws.close() is called, but before the connection is fully shut down.
During this phase, a closing handshake is performed to ensure a clean termination.
No new messages should be sent, though some buffered messages might still be processed.

Gracefully Closing a Connection

You can explicitly close a WebSocket connection using the ws.close() method. This will transition the connection through the CLOSING state (readyState = 2) before finally becoming CLOSED (readyState = 3).

Observe the state changes when closing:

const WebSocket = require('ws');
const ws = new WebSocket('ws://localhost:8080');

ws.onopen = () => {
  console.log(`Connection OPEN. State: ${ws.readyState}`); // 1
  console.log('Initiating connection close...');
  ws.close(1000, 'Client requested shutdown'); // Code 1000: normal closure
  console.log(`State after calling close(): ${ws.readyState}`); // Expected: 2 (CLOSING)
};

ws.onclose = (event) => {
  console.log(`Connection CLOSED. State: ${ws.readyState}`); // 3
  console.log(`Close Code: ${event.code}, Reason: ${event.reason}`);
};

ws.onerror = (error) => {
  console.error('Error during connection:', error.message);
};

The CLOSED State (3)

The final state for a WebSocket connection is CLOSED.

Its numeric value is 3.
The connection has been completely terminated.
No further communication can occur on this particular WebSocket object.
If you need to reconnect, you must create a new WebSocket instance.

Checking Connection Status

You can always check the current state of a WebSocket connection using its readyState property. This property returns one of the numeric values (0, 1, 2, 3) or their corresponding named constants:

WebSocket.CONNECTING (0)
WebSocket.OPEN (1)
WebSocket.CLOSING (2)
WebSocket.CLOSED (3)

Using these constants makes your code more readable!

Quick Check: Connection States

The readyState property indicates the current status of a WebSocket connection.

Recap: WebSocket Lifecycle

Great job! You've learned about the four essential states of a WebSocket connection:

CONNECTING (0): Handshake in progress.
OPEN (1): Connection established, ready for data.
CLOSING (2): Close handshake initiated.
CLOSED (3): Connection terminated.

Understanding these states is fundamental for building robust and reliable realtime applications.

الأسئلة الشائعة

هل درس «دورة حياة الاتصال وحالاته» مجاني؟

نعم — نص درس «دورة حياة الاتصال وحالاته» كامل متاح مجاناً هنا على الويب. لتمرينه بشكل تفاعلي (محرر أكواد مدمج ومدرس ذكاء اصطناعي متاح 24/7) وفتح باقي دورة WebSockets & Realtime Systems Programming، انتقل إلى CoddyKit PRO. تتضمن دورة WebSockets & Realtime Systems Programming 4 دروس في المجموع.

ماذا ستتعلم في «دورة حياة الاتصال وحالاته»؟

استكشفوا الحالات المختلفة لاتصال WebSocket، من الفتح إلى الإغلاق، وكيفية إدارتها. تتمرن على WebSockets & Realtime Systems Programming مع أكواد عملية تشغلها مباشرة في المتصفح، ومدرس ذكاء اصطناعي متاح 24/7 يجيب على أسئلتك أثناء عملك.

هل أحتاج إلى خبرة سابقة لأبدأ WebSockets & Realtime Systems Programming؟

لا تُشترط خبرة سابقة. WebSockets & Realtime Systems Programming على CoddyKit منظم للمبتدئين حتى المتقدمين، لذا يمكنك البدء من هنا أو من البداية والتقدم بسرعتك الخاصة. هذا هو الدرس 3 من أصل 4.

كم من الوقت يستغرق درس «دورة حياة الاتصال وحالاته»؟

معظم دروس CoddyKit تستغرق حوالي 5–10 دقائق. كل منها موجز وتفاعلي، لذا تحرز تقدماً مستمراً وتستأنف من حيث توقفت عبر الويب والتطبيق.

هل يمكنني كتابة وتشغيل أكواد في درس WebSockets & Realtime Systems Programming هذا؟

نعم. كل درس في WebSockets & Realtime Systems Programming يتضمن محرر أكواد مدمج، لذا تكتب وتشغل أكواداً حقيقية مباشرة في متصفحك وتحصل على تعليقات فورية من الذكاء الاصطناعي — بدون إعداد محلي.

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