WebSocket 请求-响应子协议

WebSocket 提供了像人类交谈一样的双向通信。 客户端可以向服务器发送数据，服务器可以随时向客户端发送数据。 但是请求-响应行为怎么办呢？ 客户机可以向服务器发出请求并等待响应。 Websocket 似乎没有提供任何将客户端数据(请求)链接到服务器数据(响应)的功能。

这可能是子协议的工作，我对如何做到这一点有一些想法(发送带有请求的 ID，并在超时期间等待具有相同 ID 的响应)。

为了不重新发明轮子和节省一些时间，我在互联网上寻找一个现有的解决方案，但我没有找到任何相关的(也许是坏关键字)。

有人知道这种工作吗还是我漏掉了什么？

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最佳答案

The WebSocket Application Messaging Protocol (WAMP) https://wamp-proto.org/ provides RPC (Remote Procedure Call) and PubSub (Publish & Subscribe) messaging patterns on top of raw WebSocket for that purpose.

WAMP is a proper WebSocket subprotocol, uses WebSocket as transport and JSON as a payload format. RPC is implemented using 3 messages, and those messages contain a "Call ID" to correlate asynchronous RPC server responses to client initiated procedure calls.

Disclaimer: I am author of WAMP and some (open-source) WAMP implementations. Its an open initiative, with others already started to get on the boat. Ultimately, there should be a WAMP RFC properly defining the protocol .. but its still in the early stages.

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I'm running a simple request-response program using websockets. See "Websocket Server Demonstration". You can download the webpage source code.

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take a look at the SwaggerSocket, which is a REST over WebSockets protocol supported with all major Java WebServer.

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I would use JSON-RPC 2.0.

http://www.jsonrpc.org/specification

Each message would be a JSON object. The protocol states if it is a call that wants a response (coupling with id), or a notification.

A JSON-RPC aware application could easily check if the message object contains a method, signifying a call, or not, signifying a response.

I'm about to build a javascript lib to handle json rpc over websocket, with ajax as fallback…

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Take a look at msg-rpc, it provides bidirectional rpc support over simple message interface, include WebSocket.

Not only the simple rpc, which could cover "client request / server response" behavior, it also supports "server request / client response" behavior, which is via the Rpc Service.

To get start with, there're sockjs and socket.io examples .

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(send a id with the request and wait for a reponse with the same id until a timeout period)

I created a lib that does exactly that, called WebSocketR2 (where R2 means Request Response): https://github.com/ModernEdgeSoftware/WebSocketR2

It also handles reconnecting to the server if a connection is lost, which could be helpful if you are doing web sockets through a load balancer.

The final result is you can implement callbacks on the web socket send function like this:

var request = {
action: "login",
params: {
username: "test",
password: "password"
}
};


ws.send(request, function(response){
console.log(response)
});
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A bit late on this discussion but, BrokerJS is a reactive alternative you can try in NodeJS. Define a data model and subscribe websocket connections to specific keys of the model. Any changes to server side variable are automatically reflected on the client side. I think this will save you a lot of boilerplate code. Even better, you can still use the old-fashioned websocket messaging parallel to the new reactive way of doing things. It is far from a polished product and arrays are a headache. But in conjunction with something like VueJS, React or Svelte, I think it will save you a lot of trouble.

Disclaimer: I am the the author of BrokerJS.


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