javascript - 如何从非图像的 WebSocket 读取 BLOB 数据

Question

我创建了一个到我的网络服务器的 WebSocket 连接来接收一些数据。但是，当我记录在 onmessage 函数中收到的事件时，我无法看到数据的真实内容。

当我复制我的 Chrome 浏览器 v32 打开的网络连接作为 curl 命令并在我的操作系统控制台上运行它时，一切正常。所以我认为我的 WebSocket 设置一定是错误的。 event.data 对象是 Blob 的实例。

这是我的代码(实际上是 CoffeeScript，但很容易理解):

socket = new WebSocket "wss://myserverurl/some-endpoint"

socket.onopen = (event) ->
    console.log 'Connection opened (WebSocket)'

socket.onclose = (event) ->
    console.log 'Connection closed (WebSocket)'
    code = event.code
    reason = event.reason
    wasClean = event.wasClean

socket.onmessage = (event) ->
    console.log JSON.stringify event

我得到的事件:

{
    "ports": [],
    "data": {
        "type": "",
        "size": 594
    },
    ...
    "cancelBubble": false,
    "returnValue": true,
    "srcElement": {
        "binaryType": "blob",
        "extensions": "",
        "protocol": "",
        "onerror": null,
        "bufferedAmount": 0,
        "readyState": 1
    },
    "defaultPrevented": false,
    "timeStamp": 1390578698613,
    "cancelable": false,
    "bubbles": false,
    "eventPhase": 2,
    "currentTarget": {
        "binaryType": "blob",
        "extensions": "",
        "protocol": "",
        "onerror": null,
        "bufferedAmount": 0,
        "readyState": 1
    },
    "target": {
        "binaryType": "blob",
        "extensions": "",
        "protocol": "",
        "onerror": null,
        "bufferedAmount": 0,
        "readyState": 1
    },
    "type": "message"
}

Answer 1

好的，我找到了解决方案!我必须使用 FileReader 读取作为 Blob 的数据:

socket = new WebSocket 'wss://myserverurl/some-endpoint'
socket.binaryType = 'blob'

socket.onopen = (event) ->
    console.log 'Connection opened (WebSocket)'

socket.onclose = (event) ->
    console.log 'Connection closed (WebSocket)'
    code = event.code
    reason = event.reason
    wasClean = event.wasClean

socket.onmessage = (event) ->
    if event.data instanceof Blob
        reader = new FileReader()
        reader.onload = ->
            console.log reader.result
        reader.readAsText event.data

或者，在 ES2015 中:

// Create socket
socket = new WebSocket("wss://example.org/ws");
socket.binaryType = "blob";

// Log socket opening and closing
socket.addEventListener("open", event => {
    console.log("Websocket connection opened");
});
socket.addEventListener("close", event => {
    console.log("Websocket connection closed");
});

// Handle the message
socket.addEventListener("message", event => {
    if (event.data instanceof Blob) {
        reader = new FileReader();

        reader.onload = () => {
            console.log("Result: " + reader.result);
        };

        reader.readAsText(event.data);
    } else {
        console.log("Result: " + event.data);
    }
});