I am trying to read value received from JavaScript WebSocket using Java
I have this JavaScript code:
const socket = new WebSocket("wss://localhost:7999"); // start
socket.addEventListener("open", (event) => {
socket.send("Hello!");
});
socket.addEventListener("message", (event) => {
console.log("Received message.");
});
And this Java code:
import java.io.*;
import java.net.*;
class Server {
public static void main(String[] args) throws Exception {
ServerSocket s = new ServerSocket(7999);
Socket client = s.accept();
System.out.println("I am in!");
InputStream inputStream = client.getInputStream();
InputStreamReader reader = new InputStreamReader(inputStream, "UTF-8");
BufferedReader in = new BufferedReader(reader);
String readLine;
while ((readLine = in.readLine()) != null) {
System.out.println(readLine);
}
}
}
However, upon launching the server and client code, I am receiving this value:
I am in!
���
�.isֿ���pO?��-4/P�P����- ���Q�`�:���x���wG�Z��x��v�##�6���,�+̩�0�/̨�$�#�
� �(�'����=<5/�
}�� localhost�
��http/1.1
3+)�� �-l-h������ۥ n�}�>�zUZ�Ğ�-+
My goal is to read the value Hello, that I have sent using socket.send.
Does anyone know how to fix this problem?
Thanks.
ServerSocket is quite low level construct for handling TCP connections.
Websocket even though it starts as an HTTP request it requires server to request connection upgrade, there is handshaking, then handling websocket frames, including some internal frames like ping/pong.
Unless you plan to implement that entire functionality, I'd suggest you to not use raw ServerSocket but instead use a library that provides websocket support out of the box.
Some options that I could point you to are:
netty
vert.x
Related
I'm starting with WebSockets and, to try things off, I built a minuscule WebSocket server in C# (using WebSocketSharp) and an html as a client to connect to it.
On the client I have this code:
const webSocket = new WebSocket("ws://localhost:51036/test");
webSocket.onopen = e => {
webSocket.send("hello :D");
console.log("Socket connection opened!");
}
This send() call never works — it sometimes result in an exception in the C# server, most other times it is just ignored as if nothing was ever received on the server's end. However, any send() I call afterwards (e.g. with a button) works fine, and send() inside onopen also works fine if I place it inside a timeout of just 200ms. If I don't call any send() onopen, and just call it later via a button, it always works fine (so it's not a 'first call always fails' issue).
On the C# side, the code is very simple:
public class TestWS : WebSocketBehavior {
protected override void OnMessage (MessageEventArgs e) {
System.Diagnostics.Debug.WriteLine($"Client message: {e.Data}");
Send($"String length: {e.Data.Length} [msg received: {e.Data}]");
}
}
public static class Sockets {
public const string SERVER_ROUTE = "ws://localhost:51036";
private static WebSocketServer socket;
public static void Start () {
socket = new WebSocketServer(SERVER_ROUTE);
socket.AddWebSocketService<TestWS>("/test");
socket.Start();
System.Diagnostics.Debug.WriteLine($"Server started on {SERVER_ROUTE}");
}
public static void Stop () {
socket.Stop();
}
}
The exception in question is this one:
2021-09-06 19:59:06|Fatal|WebSocket.<startReceiving>b__175_2:0|WebSocketSharp.WebSocketException: The header of a frame cannot be read from the stream.
at WebSocketSharp.WebSocketFrame.processHeader(Byte[] header)
at WebSocketSharp.WebSocketFrame.<>c__DisplayClass73_0.<readHeaderAsync>b__0(Byte[] bytes)
at WebSocketSharp.Ext.<>c__DisplayClass55_0.<ReadBytesAsync>b__0(IAsyncResult ar)
I am using JxBrowser to load a html file that resides in a jar. This html file has a websocket that is failing to connect (I receive code 106 in the onclose event)
I am getting these errors from JxBrowser
09:20:18.381 INFO: 09:20:18 SEVERE: [1228/092018.371:ERROR:validation_errors.cc(87)] Invalid message: VALIDATION_ERROR_DESERIALIZATION_FAILED
09:20:18.382 INFO: 09:20:18 SEVERE: [1228/092018.371:ERROR:render_process_host_impl.cc(4145)] Terminating render process for bad Mojo message: Received bad user message: Validation failed for WebSocket::AddChannelRequest deserializer [VALIDATION_ERROR_DESERIALIZATION_FAILED]
09:20:18.382 INFO: 09:20:18 SEVERE: [1228/092018.371:ERROR:bad_message.cc(23)] Terminating renderer for bad IPC message, reason 123
Here is my code for creating the browser
Browser browser = new Browser();
BrowserView browserView = new BrowserView(browser);
browser.addConsoleListener(new ConsoleListener() {
#Override
public void onMessage(ConsoleEvent ce) {
System.out.println("Console log from " + ce.getSource() + " message " + ce.getMessage());
}
});
BrowserContext browserContext = browser.getContext();
ProtocolService protocolService = browserContext.getProtocolService();
protocolService.setProtocolHandler("jar", new ProtocolHandler() {
#Override
public URLResponse onRequest(URLRequest request) {
try {
URLResponse response = new URLResponse();
URL path = new URL(request.getURL());
InputStream inputStream = path.openStream();
DataInputStream stream = new DataInputStream(inputStream);
byte[] data = new byte[stream.available()];
stream.readFully(data);
response.setData(data);
String mimeType = getMimeType(path.toString());
response.getHeaders().setHeader("Content-Type", mimeType);
return response;
} catch (Exception ignored) {
}
return null;
}
});
URL url = getClass().getClassLoader().getResource("resources/example.html");
browser.loadURL(url.toExternalForm());
Here is a simplified version of my WebSocket code
this.ws = new WebSocket('ws://127.0.0.0:1337');
this.ws.onopen = () => {
console.log('OnOpen');
};
this.ws.onmessage = (evt) => {
console.log('OnMessage ' + evt.data);
};
this.ws.onerror = (event) => {
console.log('OnError');
};
this.ws.onclose = (event) => {
console.log('OnClose ' + event.code + ' ' + event.reason);
};
I am having a hard time finding information on the error messages received from Chromium. Could there be problems because the URL is using the jar: protocol? Or is this a problem because chrome does not allow unsecure websocket connections?
(Edit) The socket connects when I use the JxBrowser's loadHTML method and supply the string text of the HTML file. So I believe this has something to do with the fact that I am loading from a resource URL, and not to do with chrome not allowing unsecure websocket connections. I really dont want to have to stream the file contents so that I can use loadHTML.
(Edit2) Loading the HTML from a file URL also works. I guess I can create a local copy of the HTML file in the jar and load that instead. I am disappointed that I cannot do this using the jar URL, I guess it might be a limitation of JxBrowser.
From what you described, the issue is definitely related to the URL being using the jar: protocol. Seems like websocket works only with file: http: and https: protocols.
The best solution in this case will be to read HTML from the example.html file and then load it using the loadHTML method instead of the loadURL.
I have decided to copy the HTML files from the jar into a local folder, and using a File URL to load them.
I am developing websocket server with netty frame work version 4.1.6.
I am using the sample code from netty example site
This is my server source code:
public class WebSocketServer
{
static final int PORT = 4466;
public static void main(String[] args)
{
final SslContext sslCtx;
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
SelfSignedCertificate ssc = new SelfSignedCertificate();
sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new WebSocketServerInitializer(sslCtx));
Channel ch = b.bind(PORT).sync().channel();
System.out.println("Open your web browser and navigate to " +
"http://127.0.0.1:" + PORT + '/');
ch.closeFuture().sync();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
An WebSocketServerInitializer source code:
public class WebSocketServerInitializer extends ChannelInitializer<SocketChannel>
{
private static final String WEBSOCKET_PATH = "/websocket";
private final SslContext sslCtx;
public WebSocketServerInitializer(SslContext sslCtx) {
this.sslCtx = sslCtx;
}
#Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
pipeline.addLast(sslCtx.newHandler(ch.alloc()));
pipeline.addLast(new HttpServerCodec());
pipeline.addLast(new HttpObjectAggregator(65536));
pipeline.addLast(new WebSocketServerCompressionHandler());
pipeline.addLast(new WebSocketServerProtocolHandler(WEBSOCKET_PATH, null, true));
// pipeline.addLast(new WebSocketIndexPageHandler(WEBSOCKET_PATH));
pipeline.addLast(new WebSocketFrameHandler());
}
}
This is my Html code:
<html>
<head>
<script type="text/javascript">
// Let us open a web socket
var ws = null;
function WebSocketTest()
{
if ("WebSocket" in window)
{
alert("WebSocket is supported by your Browser!");
// Let us open a web socket
ws = new WebSocket("wss://localhost:4466/websocket");
ws.onopen = function()
{
// Web Socket is connected, send data using send()
ws.send("Message to send");
alert("Message is sent...");
};
ws.onmessage = function (evt)
{
var received_msg = evt.data;
alert(received_msg);
//alert("Message is received...");
};
ws.onclose = function()
{
// websocket is closed.
alert("Connection is closed...");
};
window.onbeforeunload = function(event) {
socket.close();
};
}
else
{
// The browser doesn't support WebSocket
alert("WebSocket NOT supported by your Browser!");
}
}
</script>
</head>
<body>
<div id="sse">
Run WebSocket
</div>
</body>
</html>
I browse the page using Chrome browser and got the following message when I click on the link in the web page.
WebSocket connection to 'wss://localhost:4466/websocket' failed: Error in connection establishment: net::ERR_INSECURE_RESPONSE
According to some discussions here, and the netty websocket sample code, wss must be forwarded by HTTPS. However, when I change the following javascript statement in my web page:
ws = new WebSocket("wss://localhost:4466/websocket");
to
ws = new WebSocket("wss://echo.websocket.org");
It works fine. It make me confusing, Why the site echo.websocket.org can working without https? Why my server cannot? are there something missing in my server source code?
PS: the echo.websocket.org example found in the following url:
http://jsbin.com/muqamiqimu/edit?js,console
Your browser is failing to connect to your websocket server, because it detected it is insecure.
This happens because when the browser tries to connect to your server, it will check the SSL certificate. This certificate is basically a proof that says your server is claiming to be the authoritative server for localhost.
Your server claims this by its certificate, what in your case is signed by itself, that's basically the SelfSignedCertificate class, and it's claiming to be "example.com".
This creates 2 issues:
Your browser connects to localhost, but instead of getting a certificate for localhost, it gets 1 for example.com
Your browser does not trust the signer of the certificate to have the authority to make certificates, causing it to be rejected.
There are multiple ways to solve this:
Getting a valid certificate and hosting your application on a server
This would be the recommended solution for production, depending where you get your valid certificate, it may or may not cost money.
Bypass the certificate warning
By manually going to http://localhost:4466/ you can skip past the certificate warning, and basically this adds a 1 time exception for the certificate rule, till you restart your browser
Configuring google chrome to accept invalid certificates for localhost
While this can be insecure (but not as insecure as turning off all certificate validation), it can be a great way to test ssl on development machines.
You can turn ssl validation of for localhost by going to chrome://flags/#allow-insecure-localhost and turning that option on. Notice that you might be required to set the domain of your certificate to localhost when using this option by calling the new SelfSignedCertificate("localhost"); contructor.
I'm attempting to write a C# WebSocket server for an application that interacts upon browser input.
This is the code:
class Program {
static void Main(string[] args) {
var listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 42001);
listener.Start();
using(var client = listener.AcceptTcpClient())
using(var stream = client.GetStream())
using(var reader = new StreamReader(stream))
using(var writer = new StreamWriter(stream)) {
while (!reader.EndOfStream) {
String line = reader.ReadLine();
if (new Regex("^GET").IsMatch(line)) {
line = reader.ReadLine();
if (new Regex("^Sec-WebSocket-Key: ").IsMatch(line)) {
String key = new Regex("(^Sec-WebSocket-Key\\: |\\r\\n)").Replace(line, "");
key = Convert.ToBase64String(SHA1.Create().ComputeHash(Encoding.UTF8.GetBytes(key + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11")));
writer.WriteLine("HTTP/1.1 101 Switching Protocols");
writer.WriteLine("Upgrade: websocket");
writer.WriteLine("Connection: Upgrade");
writer.WriteLine("Sec-WebSocket-Accept: " + key);
writer.WriteLine("Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits");
writer.WriteLine("WebSocket-Origin: http://127.0.0.1");
writer.WriteLine("WebSocket-Location: ws://localhost:42001/websocket");
writer.WriteLine("");
}
}
}
}
listener.Stop();
}
}
... and:
var ws = new WebSocket('ws://localhost:42001/websocket');
ws.onopen = function() {
console.log('connected');
};
ws.onmessage = function(e) {
console.log(e.data);
};
ws.onerror = function(e) {
console.log(e);
};
ws.onclose = function() {
console.log("closed");
};
On execution, the TPCListener successfully accepts the TCPClient and reads the incoming HTTP request. It parses the Key, generates the correct Accept token, but the JS - window native - WebSocket seems to have gone flat out bonkers: it does not answer no matter what it receives.
I would expect it throwing an error upon sending a HTTP/1.1 400 Bad Request, but nothing at all happens. It just goes mute.
Checking out Chrome Dev Tools' Networking tab, I do only see the websocket outgoing GET request, but no incoming packets - is that supposed to happen?
If I forcefully close the application, WebSocket throws this exception:
WebSocket connection to 'ws://localhost:42001/websocket' failed: Error during WebSocket handshake: net::ERR_CONNECTION_RESET.
What am I missing here? Thank you all in advance.
Also, I'm not using Net.WebSockets because it is available since .NET 4.5, and my application targets systems from Windows 7 to the current build of Windows 10.
well... how far does your C# code get? My first bet would be on buffering - you don't flush the writer or stream, so I would expect them to be holding onto data while stuck in the top of the while loop, but frankly it shouldn't be a while loop in the first place - you only get one handshake per socket, not many. You could try adding flushes after the blank line, and you should make sure the Socket itself has buffering disabled (NoDelay = true;) - but: fundamentally this isn't a good way to write a web-socket server. Apart from anything else, the data will cease to be text if the handshake succeeds, so having a TextReader is a very bad thing. Frankly, you should be dealing with raw Socket / byte[] data here, IMO (having implemented this very thing several times).
So I'm building an app with a lot of web content I plan to release it using Phone Gap build but will host all the content online and will link to it. I was wondering if there is a way that the web pages can be downloaded when there is an active internet connection for offline use and when there is a connection again for the data to be refreshed preferably when the user is using a wifi connection. The site will mostly be in html, js, and php. I will be hosting with bluehost
Is there any way of doing this? Thanks in advance! Littleswany!
PhoneGap apps ARE downloaded to the device, when they are downloaded from the store. They are basically a wrapper around an index.html file, but the app is actually programmed in JavaScript, which is responsible for creating and displaying views etc. The only time you need to check for an internet connection is when you are communicating with your back end (PHP)... If the ajax request fails, the best solution is to provide the user with a button/link to try again when they have regained their internet connection, or set a timer which fires intermittently to keep trying again... NEVER use a while(true) loop in your Phone Gap app - it will just hang.
I am not familiar with java, but i think i can provide the logic to get the job done.
You want to do an infinite loop that checks if the user is on wifi. Then if true, use wget, rsync, or scp to download the website. Something like this.:
while (true){
// do an if statement that checks if user is on wifi. Then do a then statement that uses rsync or wget.
}
Info on how to nest if statements in while loops in java: java loop, if else
I do not know if wget, rsync, or scp can be ran from java. You'll need to look more into it or write your own alternative function to do it. Something like:
function download_file() {
var url = "http://www.example.com/file.doc"
window.location = url;
}
You should be able to do it from your java like this:
String whatToRun = "/usr/local/bin/wget http://insitu.fruitfly.org/insitu_image_storage/img_dir_38/insitu38795.jpe";
Sources:
1. What is the equivalent of wget in javascript to download a file from a given url?
2. Call a command in terminal using Java (OSX)
First Create an Connection filter class
public class Connection_Status{
private static ConnectivityManager connectivityManager;
static boolean connected = false;
public static Boolean isOnline(Context ctx) {
try {
connectivityManager = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
connected = networkInfo != null && networkInfo.isAvailable()&& networkInfo.isConnected();
return connected;
} catch (Exception e) {
System.out.println("CheckConnectivity Exception: " + e.getMessage());
}
return connected;
}
}
And in your Main class
public class Main extends Activity{
private WebView mWebView;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mWebView = (WebView) findViewById(R.id.webview);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setBuiltInZoomControls(true);
if(Connection_Status.isOnline(Main.this)){
HttpClient httpclient = new DefaultHttpClient(); // Create HTTP Client
HttpGet httpget = new HttpGet("http://yoururl.com"); // Set the action you want to do
HttpResponse response = httpclient.execute(httpget); // Executeit
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent(); // Create an InputStream with the response
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) // Read line by line
sb.append(line + "\n");
String resString = sb.toString(); //
is.close(); // Close the stream
}
}
}
Or you can use cache on it e.g
mWebView.getSettings().setAppCacheMaxSize(1024*1024*8);
mWebView.getSettings().setAppCachePath(""+this.getCacheDir());
mWebView.getSettings().setAppCacheEnabled(true);
mWebView.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);
Don't forget to add the following permissions
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> <!-- for the connection status-->
Sources:
https://stackoverflow.com/a/6503817/1309629