Real-Time Data Communication Technologies

WHAT IS SIGNALR?

SignalR is an open-source library developed by Microsoft that enables the development of real-time applications. This library is used to facilitate instant communication between the server and clients. Real-time communication is a type of interaction where an action performed by one user is immediately reflected to other users. SignalR automates connection management and broadcasts messages to all connected clients, making real-time communication possible. This ensures that the connection between the server and clients remains continuously open, allowing communication to happen instantly. Additionally, private communication targeting specific messages among clients can be achieved.

In contrast to traditional HTTP connections, SignalR keeps connections persistent. This means that once a connection is established, it remains open continuously without being reestablished repeatedly. This feature improves user experience and provides more effective communication in real-time applications. The working principle of SignalR involves the use of a script on the client side to create a bridge between the server and client, facilitating communication. The client sends an HTTP request to the server, the server processes the request, and then responds to the client. This process enables instant communication, allowing users to respond immediately to events in the application. SignalR is commonly used as a preferred technology for implementing real-time features in web applications, such as live chat, real-time updates, and notification systems.

SIGNALR DATA TRANSFER TYPES (TRANSPORTS)

WEBSOCKET WebSocket is a communication protocol that supports real-time, bidirectional communication in web applications. Unlike the HTTP protocol, it allows data transmission over a continuous connection, resulting in lower latency and more efficient communication. WebSocket is commonly used in applications such as live chat, games, financial applications, and other real-time applications.

WORKING STEPS:

• Handshake (Connection Establishment): Initially, the client sends an HTTP request to the server to establish a WebSocket connection. This request comes with an "Upgrade" header, and if the server supports WebSocket connections, it responds positively.
• Bidirectional Communication: Once the connection is established, both parties can send data over the connection at any time. When the client or server sends data, the other party can immediately receive this data.
• Closing and Error Conditions: The client or server can send special closing frames to close the connection or report an error.
• Full Bidirectional Communication: Both parties can independently send and receive data over the connection. The server can send data to all connected clients, not just a specific client.
• Low-Level TCP Connection: WebSocket is built on a low-level TCP connection, providing more efficient and lower-latency communication.

SERVER-SENT EVENTS (SSE) Server-Sent Events (SSE) is a web technology that provides unidirectional (only from the server to the client) real-time communication. SSE is particularly used in applications that require instant notifications and updates.

WORKING STEPS:

• Handshake (Connection Establishment): The client sends an HTTP GET request to the server, using the "text/event-stream" media type. The server accepts this request and responds to the client.
• Unidirectional Communication: As long as the connection is open, the server continues to send data to the client at specified intervals. The sent data consists of special formatted messages like "data:", "event:", "id:", "retry:".
• Data Sending: When a specific event occurs or there is new data, the server sends this information to the client in a "data:" message. The client receives and processes this data appropriately.
• Retry Mechanism: If the connection is lost or an error occurs, the server can send a "retry:" message with a time interval for the client to re-establish the connection.
• Connection Control: To maintain a sustainable connection, the server can send "ping" messages at regular intervals. The client responds to these "ping" messages to keep the connection alive.

LONG POLLING Long Polling is a communication method where, instead of establishing a continuous connection between the server and the client, the client continuously sends HTTP requests to the server and waits for a response.

WORKING STEPS:

• Client Requests: The client sends an HTTP GET request to the server. The server receives this request but does not respond immediately.
• Response When Data is Ready: The server responds to this request when a specific event occurs or there is new data. After the client receives and processes the response, it sends a new request. This process is repeated continuously, and the connection is closed and restarted each time.
• Timeout and Restart: If the server cannot send new data for a certain period, it responds to the request and closes the connection. The client, after a certain time (timeout), sends a new request to restart the connection.

USE CASES:

• GAMES: To provide real-time interaction in multiplayer games.
• CHAT APPLICATIONS: To support live chats in instant messaging applications.
• REAL-TIME NOTIFICATION SYSTEMS: To send fast and up-to-date notifications to users.
• FINANCIAL TRANSACTIONS: To share and update real-time financial data.

Adil ALATAŞ