HTTP Programming

HTTP, as a universal application-layer protocol, facilitates data transmission through a request-response mechanism where the client sends requests and the server returns responses. The format of requests and responses is fixed, consisting of a header and a body.

The most commonly used request types are GET and POST. A GET request contains only a header and is used to request application-layer data from the server. A POST request includes a body, separated from the header by an empty line, and is used to provide application-layer data to the server.

The header fields of request-response messages are numerous and will not be exhaustively detailed here. Cangjie supports HTTP protocol versions 1.0/1.1/2.0, among others. Developers can construct request and response messages based on RFCs 9110, 9112, 9113, 9218, 7541, and the HttpRequestBuilder and HttpResponseBuilder classes provided by Cangjie.

The following example demonstrates how to use Cangjie for client and server programming. The functionality implemented involves the client sending a request with the header GET /hello, and the server returning a response with the body "Hello Cangjie!". The code is as follows:

Note:

Libraries such as net and log have been moved from the Cangjie SDK to the stdx module. Before use, download the software package and configure it in cjpm.toml.

import stdx.net.http.*
import std.time.*
import std.sync.*
import stdx.log.*

// 1. Build a Server instance
let server = ServerBuilder()
    .addr("127.0.0.1")
    .port(0)
    .build()

func startServer(): Unit {
    // 2. Register request handling logic
    server.distributor.register("/hello", {httpContext =>
        httpContext.responseBuilder.body("Hello Cangjie!")
    })
    server.logger.level = LogLevel.OFF
    // 3. Start the service
    server.serve()
}

func startClient(): Unit {
    // 1. Build a client instance
    let client = ClientBuilder().build()
    // 2. Send a request
    let response = client.get("http://127.0.0.1:${server.port}/hello")
    // 3. Read the response body
    let buffer = Array<Byte>(32, repeat: 0)
    let length = response.body.read(buffer)
    println(String.fromUtf8(buffer[..length]))
    // 4. Close the connection
    client.close()
}

main () {
    spawn {
        startServer()
    }
    sleep(Duration.second)
    startClient()
}

Compiling and executing the above code will print:

Hello Cangjie!