连接到 Python websockets 时出现 Ktor MalformedInputException

Question

我正在尝试组织 python 服务器和 kotlin 客户端之间的 websocket 连接。作为 websockets 库，我使用 websockets 和 ktor。我写了两个简单的测试应用程序。因此，当我尝试从服务器获取响应文本时，我得到了 MalformedInputException。由于调试过程，我使用 Node js 编写了简单的 websocket 服务器，它工作正常。 我想我的编码有问题，但不知道如何解决。

Python 服务器

import asyncio
import websockets
from websockets import WebSocketServerProtocol

class Server:

    async def __respond(self, client: WebSocketServerProtocol, message: str):
        print(message)
        await client.send(message)

    async def ws_handler(self, client: WebSocketServerProtocol, uri: str) -> None:
        async for message in client:
            await self.__respond(client, message)

server = Server()
start_server = websockets.serve(server.ws_handler, '127.0.0.1', 4000)
loop = asyncio.get_event_loop()
loop.run_until_complete(start_server)
loop.run_forever()

Kotlin 客户端

client.ws(
            method = HttpMethod.Get,
            host = "127.0.0.1",
            port = 4000,
            path = "/ws",
            request = {
                header("Sec-WebSocket-Extensions", "permessage-deflate")
            }
        ) {
            send(Frame.Text("message"))

            for (frame in incoming) {
                when (frame) {
                    is Frame.Text -> println(frame.readText())
                    is Frame.Binary -> println(String(frame.readBytes(), StandardCharsets.UTF_8))
                    else -> println("error")
                }
            }
        }

Kotlin 堆栈跟踪

io.ktor.utils.io.charsets.MalformedInputException: Input length = 1
    at io.ktor.utils.io.charsets.CharsetJVMKt.throwExceptionWrapped(CharsetJVM.kt:325)
    at io.ktor.utils.io.charsets.CharsetJVMKt.decode(CharsetJVM.kt:199)
    at io.ktor.utils.io.charsets.EncodingKt.decode(Encoding.kt:103)
    at io.ktor.utils.io.charsets.EncodingKt.decode$default(Encoding.kt:101)
    at io.ktor.http.cio.websocket.FrameCommonKt.readText(FrameCommon.kt:146)
    at com.veronica.service.Client$run$3.invokeSuspend(Client.kt:33)

在“is Frame.Text -> println(frame.readText())”行抛出异常

Ktor 版本是 1.6.0

Answer 1

要使其正常工作，请安装 WebSocket Deflate extension:

HttpClient(CIO) {
    install(WebSockets) {
        extensions {
            install(WebSocketDeflateExtension) {
                compressionLevel = Deflater.DEFAULT_COMPRESSION
                compressIfBiggerThan(bytes = 4 * 1024)
            }
        }
    }
}

并删除设置Sec-WebSocket-Extensions标头的代码：

request = {
    header("Sec-WebSocket-Extensions", "permessage-deflate")
}