[英]Sending binary data over websocket with cowboy and MessagePack
I'm trying to send a MessagePack-encoded message from Cowboy to a browser over WebSocket, and received data is always empty or invalid. 我正在尝试通过WebSocket将来自Cowboy的MessagePack编码消息发送到浏览器,并且接收到的数据始终为空或无效。 I'm able to send binary data from JS to my cowboy handler, but not vice versa. 我能够将JS中的二进制数据发送给我的牛仔处理程序,但反之亦然。 I'm using Cowboy 1.0.4 with official msgpack-erlang
application. 我正在使用Cowboy 1.0.4与官方的msgpack-erlang
应用程序。 I also use msgpack-lite
for my in-browser javascript. 我也使用msgpack-lite
作为我的浏览器中的javascript。
Examples: 例子:
websocket_handler
: websocket_handler
:
websocket_handle({text, <<"return encoded">>}, Req, State) ->
%% sends encoded message to client. Client is unable to decode and fails
{reply, {binary, msgpack:pack(<<"message">>)}, Req, State};
websocket_handle({binary, Encoded}, Req, State) ->
%% Works as expected
lager:info("Received encoded message: ~p", [msgpack:unpack(Encoded)]),
{ok, Req, State};
JS: JS:
var host = "ws://" + window.location.host + "/websocket";
window.socket = new WebSocket(host);
socket.binaryType = 'arraybuffer';
socket.onmessage = function(event) {
var message = msgpack.decode(event.data);
console.log(message);
};
Browser returns an error inside msgpack.min.js: 浏览器在msgpack.min.js中返回错误:
Error: Invalid type: undefined
...ion n(t){var r=i(t),e=f[r];if(!e)throw new Error("Invalid type: "+(r?"0x"+r.toSt...
If I try to output raw event.data to console, here's what I'm getting: 如果我尝试将原始event.data输出到控制台,这是我得到的:
ArrayBuffer {}
It seems to be empty for some reason. 由于某种原因,它似乎是空的。 I'm new both to erlang
and msgpack
, and don't know what is going wrong. 我是erlang
和msgpack
,不知msgpack
什么问题。 Thanks for your help! 谢谢你的帮助!
Found the reason of my problem. 找到了我的问题的原因。 The way how I tried to decode message on the client was wrong: 我尝试在客户端上解码消息的方式是错误的:
socket.onmessage = function(event) {
var message = msgpack.decode(event.data);
console.log(message);
};
The right way: 正确的方式:
socket.onmessage = function(event) {
var raw_binary_data = new Uint8Array(event.data);
var message = msgpack.decode(raw_binary_data);
console.log(message);
};
It seems like msgpack-lite
doesn't support binary type. 似乎msgpack-lite
不支持二进制类型。 Try pack your data as a string. 尝试将数据打包为字符串。
{binary, msgpack:pack("message", [{enable_str, true}])}
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