You can use networking in Web in the following two ways:
Optionally, you can use WebSockets or WebRTC from JavaScript to implement your own networking. You can’t use any .NET networking classes within the Web platform because JavaScript code doesn’t have direct access to internet protocol (IP) sockets to implement network connectivity. Specifically, Web doesn’t support any .NET classes within the System.Net namespace.
Unity supports the UnityWebRequest class in WebGL. To implement the UnityWebRequest class, Unity uses the JavaScript Fetch API, which uses the browser to handle web requests. This imposes security restrictions on accessing cross-domain resources.
If you send a web request to a server other than the one that hosts the Unity content, the server you’re sending it to must authorize the Unity content.
为了在 WebGL 中访问跨域 Web 资源，您尝试访问的服务器需要使用跨源资源共享 (CORS) 对此跨域 Web 资源进行授权。
If you try to access content using UnityWebRequest, and the remote server doesn’t have CORS set up or configured correctly, an error like the following appears in the browser console:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://myserver.com/.This can be fixed by moving the resource to the same domain or enabling CORS.
服务器需要向发出的 http 响应中添加一些 Access-Control 标头，以指示哪些网页有权从 Web 浏览器读取该信息。
For a demonstration of how to add Access-Control headers that allow Unity Web to access resources on a web server from any origin, refer to the following example. This example includes common request headers and allows the GET, POST or OPTIONS methods:
"Access-Control-Allow-Credentials": "true",
"Access-Control-Allow-Headers": "Accept, X-Access-Token, X-Application-Name, X-Request-Sent-Time",
"Access-Control-Allow-Methods": "GET, POST, OPTIONS",
"Access-Control-Allow-Origin": "*",
Don’t use code that blocks a UnityWebRequest download, such as this:
while(!www.isDone) {}
You can’t block the thread to wait for a UnityWebRequest download to finish otherwise your application freezes. Because WebGL is single threaded, and the fetch API in JavaScript is asynchronous, your download might not finish unless you return control to the browser. Instead, use a Coroutine and a yield statement to wait for the download to finish. For more information, see Examples of coroutines using UnityWebRequest.
Unity Multiplayer enables communication via the WebSockets protocol. Refer to NetworkServer.useWebSockets.
WebGL doesn’t allow direct access to IP sockets, but you can use WebSockets or WebRTC (the two most common networking protocols supported by browsers) to get around this. While WebSockets are widely supported, WebRTC allows peer-to-peer connections between browsers and unreliable connections. Unity doesn’t have a built-in API that allows you to use WebSockets or WebRTC, but you can use a JavaScript plug-in to implement this. You can find plug-ins that implement WebSocket networking on the Unity Asset Store.