Building Websocket in C++ Without Boost: A Comprehensive Guide

Websockets are a popular choice for real-time web applications and are widely used across different programming languages. In C++, Boost is the go-to library for implementing websockets. However, many developers prefer to avoid Boost due to its large size and complexity. In this article, we will explore how to implement websockets in C++ without Boost.

What are Websockets?

Websockets are a protocol that enables real-time communication between a client and a server. Unlike traditional HTTP requests, websocket connections are kept open, allowing for bidirectional communication between the client and server.

Websockets are widely used for real-time applications, such as chat applications, gaming, and financial trading platforms. They are also used in IoT applications for real-time data transfer between devices.

Why Avoid Boost?

Boost is a popular C++ library that provides a wide range of functionality, including websockets. Boost is a large library, consisting of over 80 modules, and can add significant bloat to your application. Additionally, Boost can be complex and difficult to use, especially for beginners.

For these reasons, many developers prefer to avoid Boost and instead use lightweight libraries or roll their own implementation.

Implementing Websockets in C++

Implementing websockets in C++ can be a daunting task, especially without the help of a library like Boost. However, with the right approach, it is possible to create a robust websocket implementation in C++.

Step 1: Create a TCP Server

The first step in implementing websockets is to create a TCP server that listens for incoming connections. This server will handle the initial handshake with the client and upgrade the connection to a websocket connection.

To create a TCP server in C++, we can use the standard library’s socket and accept functions. Here is an example of a simple TCP server that listens on port 8080:

1. Create a socket using the socket function:

int serverSocket = socket(AF_INET, SOCK_STREAM, 0);

2. Bind the socket to a port using the bind function:

sockaddr_in serverAddress; serverAddress.sin_family = AF_INET; serverAddress.sin_port = htons(8080); serverAddress.sin_addr.s_addr = INADDR_ANY; bind(serverSocket, (struct sockaddr *) &serverAddress, sizeof(serverAddress));

3. Listen for incoming connections using the listen function:

listen(serverSocket, 5);

4. Accept incoming connections using the accept function:

sockaddr_in clientAddress; socklen_t clientAddressLength = sizeof(clientAddress); int clientSocket = accept(serverSocket, (struct sockaddr *) &clientAddress, &clientAddressLength);

Step 2: Handle the Handshake

Once a client connects to our TCP server, we need to handle the initial handshake to upgrade the connection to a websocket connection. The handshake involves sending an HTTP response to the client with a special header that indicates that the connection is being upgraded to a websocket connection.

To handle the handshake, we need to parse the incoming HTTP request from the client and generate an appropriate response. Here is an example of a simple handshake implementation:

1. Read the initial HTTP request from the client:

char buffer[1024]; int bytesRead = recv(clientSocket, buffer, sizeof(buffer), 0);

2. Parse the HTTP request to extract the key:

std::string key; // Extract the key from the HTTP request

3. Generate the HTTP response with the upgraded connection header:

std::ostringstream responseStream; responseStream << "HTTP/1.1 101 Switching Protocols\r\n"; responseStream << "Upgrade: websocket\r\n"; responseStream << "Connection: Upgrade\r\n"; responseStream << "Sec-WebSocket-Accept: " << calculateWebSocketAccept(key) << "\r\n"; responseStream << "\r\n"; std::string response = responseStream.str();

4. Send the HTTP response to the client:

send(clientSocket, response.c_str(), response.length(), 0);

Step 3: Implement the Websocket Protocol

Once the handshake is complete, we can start sending and receiving data over the websocket connection. The websocket protocol involves a series of frames that are sent between the client and server.

To implement the websocket protocol, we need to handle the following tasks:

• Parsing incoming frames from the client
• Generating outgoing frames to send to the client
• Handling various types of frames, such as text and binary frames
• Handling control frames, such as ping and close frames

Here is an example of a simple websocket implementation that can handle text frames:

1. Read an incoming frame from the client:

char buffer[1024]; int bytesRead = recv(clientSocket, buffer, sizeof(buffer), 0);

2. Parse the incoming frame to extract the payload:

std::string payload; // Parse the incoming frame to extract the payload

3. Create an outgoing frame with the payload:

std::ostringstream frameStream; frameStream << (char) 0x81; // Text frame frameStream << (char) (payload.length() & 0x7F); // Payload length frameStream << payload; // Payload data std::string frame = frameStream.str();

4. Send the outgoing frame to the client:

send(clientSocket, frame.c_str(), frame.length(), 0);

Conclusion

Implementing websockets in C++ without Boost is a challenging task, but it can be done with the right approach. By creating a TCP server, handling the handshake, and implementing the websocket protocol, we can create a robust websocket implementation in C++.

FAQs

What is Boost?

Boost is a popular C++ library that provides a wide range of functionality, including websockets. However, Boost can be large and complex, making it difficult to use for some developers.

Why avoid Boost?

Many developers prefer to avoid Boost due to its large size and complexity. Additionally, some developers prefer to use lightweight libraries or roll their own implementation for greater control over their code.

What are websockets used for?

Websockets are used for real-time web applications, such as chat applications, gaming, and financial trading platforms. They are also used in IoT applications for real-time data transfer between devices.