Netty wss socket client drops connection - sockets

Question

Trying to setup basic wss client. Channel is activated, but then immediately disconnected without any exception.
Client:
class WebSocketClient(val uri: String) {
lateinit var ch: Channel
fun connect() {
val bootstrap = Bootstrap()
val uri: URI = URI.create(uri)
val handler = WebSocketClientHandler(WebSocketClientHandshakerFactory.newHandshaker(uri, WebSocketVersion.V13, null, false, HttpHeaders.EMPTY_HEADERS, 1280000))
bootstrap.group(NioEventLoopGroup())
.channel(NioSocketChannel::class.java)
.handler(object : ChannelInitializer<SocketChannel>() {
override fun initChannel(ch: SocketChannel) {
val pipeline = ch.pipeline()
pipeline.addLast("http-codec", HttpClientCodec())
pipeline.addLast("aggregator", HttpObjectAggregator(65536))
pipeline.addLast("ws-handler", handler)
}
})
ch = bootstrap.connect(uri.host, 443).sync().channel()
handler.channelPromise.sync()
}
}
Handler:
class WebSocketClientHandler(val handShaker: WebSocketClientHandshaker) : SimpleChannelInboundHandler<Any>() {
lateinit var channelPromise: ChannelPromise
override fun handlerAdded(ctx: ChannelHandlerContext) {
channelPromise = ctx.newPromise()
}
override fun channelActive(ctx: ChannelHandlerContext) {
handShaker.handshake(ctx.channel())
}
override fun channelRead0(ctx: ChannelHandlerContext, msg: Any) {
val ch = ctx.channel()
if (!handShaker.isHandshakeComplete) {
handShaker.finishHandshake(ch, msg as FullHttpResponse)
channelPromise.setSuccess()
return
}
val frame = msg as WebSocketFrame
if (frame is TextWebSocketFrame) {
println("text message: $frame")
} else if (frame is PongWebSocketFrame) {
println("pont message")
} else if (frame is CloseWebSocketFrame) {
ch.close()
} else {
println("unhandled frame: $frame")
}
}
}
The flow of handler calls:
handleAdded
channelRegistered
channelActive
channelReadComplete
channelInactive
channelUnregistered
handlerRemoved
Is there something I miss?

Answer 1

You forgot to add a SSLHandler, this handler is needed because you are connecting to the https port (443), so the remote server expects all the traffic to be encrypted. Sending a unencrypted message to the https port has undefined behaviour, some server will shut down your connection, other servers will send a redirect back to https.
You can add an sslhandler using the following way:
java:
final SslContext sslCtx = SslContextBuilder.forClient()
// .trustManager(InsecureTrustManagerFactory.INSTANCE)
.build();
pipeline.addLast("ssl-handler", sslCtx.newHandler(ch.alloc(), url.getHost(), 443));
// Your remaining code....
pipeline.addLast("http-codec", new HttpClientCodec())