A lightweight HTTP server library written in Swift for iOS/macOS/tvOS.

What's New

1.0.0 - Fresh start


First public release.


Aoxiang(翱翔) is a lightweight HTTP server library written in Swift for iOS/macOS/tvOS.


  • Lightweight, Zero-dependency
  • Asynchronous, Non-blocking
  • Support HTTP/1.1
  • Support HTTP chunked transfer encoding (streaming)
  • Support SSE (Server-Sent Events)
  • Middleware support
  • Friendly API, keep it simple and easy to use

Hello World

import Aoxiang

let server = HTTPServer()

server.get("/") { req, res in
    res.send("Hello World!")

try server.start(8080)

Then open your browser and visit http://localhost:8080/ to see the result.

Basic routing

Routing refers to how an application’s endpoints (URIs) respond to client requests. You define routing using methods of the HTTPServer instance that correspond to HTTP methods; for example, get() to handle GET requests and post() to handle POST requests.

The following examples illustrate defining simple routes.

Respond with Hello World! on the homepage:

server.get("/") { req, res in
    res.send("hello Aoxiang!")

Respond to POST request on the homepage:"/") { req, res in
    res.send("Got a POST request")

Respond to a PUT request to the /user route:

server.put("/user") { req, res in
    res.send("Got a PUT request at /user")

Respond to a DELETE request to the /user route:

server.delete("/user") { req, res in
    res.send("Got a DELETE request at /user")


Aoixang supports async/await to handle asynchronous operations, it makes your code more readable and easier to maintain.

server.get("/async") { req, res async in
    let user = await readUserInfo()


Middleware functions are functions that have access to the HTTP request(req) and response(res) objects, and the next function in the application’s request-response cycle. The next function is a function in the router which, when invoked, executes the middleware succeeding the current middleware.

Middleware functions can perform the following tasks:

  • Execute any code.
  • Make changes to the request and the response objects.
  • End the request-response cycle.
  • Call the next middleware in the stack.

You can use middleware for many purposes in your web application, for example:

  • Logging
  • Authentication
  • Error handling
  • ...

Aoxiang supports middleware like Express. You can use use() to add middleware to your server.

This example shows a middleware function with no mount path. The function is executed every time the app receives a request.

server.use { req, res, next in
    print("Time: \(Date())")

Also you can use HTTPMiddleware to implement middleware.

class TimeMiddleware: HTTPMiddleware {
    override func handle(_ req: HTTPRequest, _ res: HTTPResponse, next: @escaping () -> Void) {
        print("Time: \(Date())")


The order of middleware loading is important: middleware functions that are loaded first are also executed first.

Chunked streaming

Aoxiang supports HTTP chunked transfer encoding out of the box. You can use write() to send chunked data to client, and use end() to end the response.

server.get("/stream") { _, res in
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {

SSE(Server-Sent Events)

Aoxiang supports SSE(Server-Sent Events) out of the box. You can use sendEvents() to get a EventSource and send events to client. don't forget to call close() to close the connection.

server.get("/sse") { req, res in
    let target = res.sendEvents()
    target.dispatchMessage("SSE Response:")
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
        target.dispatchMessage("chunk 1")

Change response header

Aoxiang provides a headers property to help you change response header, you can set it before call send() or write().

This example shows how to set a single header:"/send") { req, res in
    res.headers["Access-Control-Allow-Origin"] = "*"
    // ...

This example shows how to set HTTP status code:"/send") { req, res in
    res.statusCode = 404
    // ...

For more customization, you can check HTTPResponse class.


Swift Package Manager

  • File > Swift Packages > Add Package Dependency
  • Add
  • Select "Up to Next Major" with "1.0.0"

or add the following to your Package.swift file:

dependencies: [
    .package(url: "", .upToNextMajor(from: "1.0.0"))


Why named Aoxiang?

Aoxiang(翱翔) means "soar" in Chinese. I hope this library can help you to build your own web server lightweight and easily.

res.send() vs res.write()

  • res.write() is used to send chunked data to client, it will keep the connection alive, until you call res.end() manually.
  • res.send() is used to send data to client, it will close the connection after sending data automatically.


You are welcome to contribute to this project. Fork and make a Pull Request, or create an Issue if you see any problem.


Aoxiang is released under the MIT license. See LICENSE for details.


  • Swift Tools 5.4.0
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Last updated: Wed Mar 20 2024 19:17:53 GMT-0900 (Hawaii-Aleutian Daylight Time)