Develop Reference

Receive mails from Inbox on startup with Integration Mail

As already said in the title I'm looking for a way to receive mails with Integration Mail on Startup. Due to restrictions in the system I'm working in, the only way to get the mails is over the inbox and i should preferable only do it with integration mail. I know its possible with Javax.Mail, but its a lot of lines for just reading out the old mails on program start. I tired to do do it with a SearchTermStrategy with looking for already seen mails, but that ends up in a loop of reading old mails. Anybody knows a way to do it with integration mail?
I got a integration flow that constantly listens for mails, and i tried to do
do do one that reads out all the read mails, so i can keep track of them, the only problem with that is, that it checks for old mails via the SEEN Flag, and it cant differentiate between mails it already read out once that way, so it keeps reading out the same mails.
I also tried it with ImapMailReceiver(url).setSearchTermStrategy(searchTermStrategy())
with the strategy to get unseen mails, from trying with the debugger i saw there might be messages in the ImapMailReceiver, but I got no clue how to access them or if i can access those.
That's what I tried so far.

See MailReceivingMessageSource and something like OnlyOnceTrigger to let Inbound Channel Adapter to work only once on startup. After only one execution it is not going to look into the source any more:
public class OnlyOnceTrigger implements Trigger {
private final AtomicBoolean hasRun = new AtomicBoolean();
#Override
public Date nextExecutionTime(TriggerContext triggerContext) {
return this.hasRun.getAndSet(true) ? null : new Date();
}
}
I don't think the ImapIdleChannelAdapter is a good choice for this kind of tasks.

PDF File Transfer from server to client: "java.io.IOException: An existing connection was forcibly closed by the remote host" [duplicate]

I am working with a commercial application which is throwing a SocketException with the message,
An existing connection was forcibly closed by the remote host
This happens with a socket connection between client and server. The connection is alive and well, and heaps of data is being transferred, but it then becomes disconnected out of nowhere.
Has anybody seen this before? What could the causes be? I can kind of guess a few causes, but also is there any way to add more into this code to work out what the cause could be?
Any comments / ideas are welcome.
... The latest ...
I have some logging from some .NET tracing,
System.Net.Sockets Verbose: 0 : [8188] Socket#30180123::Send() DateTime=2010-04-07T20:49:48.6317500Z
System.Net.Sockets Error: 0 : [8188] Exception in the Socket#30180123::Send - An existing connection was forcibly closed by the remote host DateTime=2010-04-07T20:49:48.6317500Z
System.Net.Sockets Verbose: 0 : [8188] Exiting Socket#30180123::Send() -> 0#0
Based on other parts of the logging I have seen the fact that it says 0#0 means a packet of 0 bytes length is being sent. But what does that really mean?
One of two possibilities is occurring, and I am not sure which,
The connection is being closed, but data is then being written to the socket, thus creating the exception above. The 0#0 simply means that nothing was sent because the socket was already closed.
The connection is still open, and a packet of zero bytes is being sent (i.e. the code has a bug) and the 0#0 means that a packet of zero bytes is trying to be sent.
What do you reckon? It might be inconclusive I guess, but perhaps someone else has seen this kind of thing?

This generally means that the remote side closed the connection (usually by sending a TCP/IP RST packet). If you're working with a third-party application, the likely causes are:
You are sending malformed data to the application (which could include sending an HTTPS request to an HTTP server)
The network link between the client and server is going down for some reason
You have triggered a bug in the third-party application that caused it to crash
The third-party application has exhausted system resources
It's likely that the first case is what's happening.
You can fire up Wireshark to see exactly what is happening on the wire to narrow down the problem.
Without more specific information, it's unlikely that anyone here can really help you much.

Using TLS 1.2 solved this error.
You can force your application using TLS 1.2 with this (make sure to execute it before calling your service):
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
Another solution :
Enable strong cryptography in your local machine or server in order to use TLS1.2 because by default it is disabled so only TLS1.0 is used.
To enable strong cryptography , execute these commande in PowerShell with admin privileges :
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type DWord
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type DWord
You need to reboot your computer for these changes to take effect.

This is not a bug in your code. It is coming from .Net's Socket implementation. If you use the overloaded implementation of EndReceive as below you will not get this exception.
SocketError errorCode;
int nBytesRec = socket.EndReceive(ar, out errorCode);
if (errorCode != SocketError.Success)
{
nBytesRec = 0;
}

Had the same bug. Actually worked in case the traffic was sent using some proxy (fiddler in my case). Updated .NET framework from 4.5.2 to >=4.6 and now everything works fine. The actual request was:
new WebClient().DownloadData("URL");
The exception was:
SocketException: An existing connection was forcibly closed by the
remote host

Simple solution for this common annoying issue:
Just go to your ".context.cs" file (located under ".context.tt" which located under your "*.edmx" file).
Then, add this line to your constructor:
public DBEntities()
: base("name=DBEntities")
{
this.Configuration.ProxyCreationEnabled = false; // ADD THIS LINE!
}

I've got this exception because of circular reference in entity.In entity that look like
public class Catalog
{
public int Id { get; set; }
public int ParentId { get; set; }
public Catalog Parent { get; set; }
public ICollection<Catalog> ChildCatalogs { get; set; }
}
I added [IgnoreDataMemberAttribute] to the Parent property. And that solved the problem.

If Running In A .Net 4.5.2 Service
For me the issue was compounded because the call was running in a .Net 4.5.2 service. I followed #willmaz suggestion but got a new error.
In running the service with logging turned on, I viewed the handshaking with the target site would initiate ok (and send the bearer token) but on the following step to process the Post call, it would seem to drop the auth token and the site would reply with Unauthorized.
Solution
It turned out that the service pool credentials did not have rights to change TLS (?) and when I put in my local admin account into the pool, it all worked.

I had the same issue and managed to resolve it eventually. In my case, the port that the client sends the request to did not have a SSL cert binding to it. So I fixed the issue by binding a SSL cert to the port on the server side. Once that was done, this exception went away.

For anyone getting this exception while reading data from the stream, this may help. I was getting this exception when reading the HttpResponseMessage in a loop like this:
using (var remoteStream = await response.Content.ReadAsStreamAsync())
using (var content = File.Create(DownloadPath))
{
var buffer = new byte[1024];
int read;
while ((read = await remoteStream.ReadAsync(buffer, 0, buffer.Length)) != 0)
{
await content.WriteAsync(buffer, 0, read);
await content.FlushAsync();
}
}
After some time I found out the culprit was the buffer size, which was too small and didn't play well with my weak Azure instance. What helped was to change the code to:
using (Stream remoteStream = await response.Content.ReadAsStreamAsync())
using (FileStream content = File.Create(DownloadPath))
{
await remoteStream.CopyToAsync(content);
}
CopyTo() method has a default buffer size of 81920. The bigger buffer sped up the process and the errors stopped immediately, most likely because the overall download speeds increased. But why would download speed matter in preventing this error?
It is possible that you get disconnected from the server because the download speeds drop below minimum threshold the server is configured to allow. For example, in case the application you are downloading the file from is hosted on IIS, it can be a problem with http.sys configuration:
"Http.sys is the http protocol stack that IIS uses to perform http communication with clients. It has a timer called MinBytesPerSecond that is responsible for killing a connection if its transfer rate drops below some kb/sec threshold. By default, that threshold is set to 240 kb/sec."
The issue is described in this old blogpost from TFS development team and concerns IIS specifically, but may point you in a right direction. It also mentions an old bug related to this http.sys attribute: link
In case you are using Azure app services and increasing the buffer size does not eliminate the problem, try to scale up your machine as well. You will be allocated more resources including connection bandwidth.

I got the same issue while using .NET Framework 4.5. However, when I update the .NET version to 4.7.2 connection issue was resolved. Maybe this is due to SecurityProtocol support issue.

For me, it was because the app server I was trying to send email from was not added to our company's SMTP server's allowed list.
I just had to put in SMTP access request for that app server.
This is how it was added by the infrastructure team (I don't know how to do these steps myself but this is what they said they did):
1. Log into active L.B.
2. Select: Local Traffic > iRules > Data Group List
3. Select the appropriate Data Group
4. Enter the app server's IP address
5. Select: Add
6. Select: Update
7. Sync config changes

Yet another possibility for this error to occur is if you tried to connect to a third-party server with invalid credentials too many times and a system like Fail2ban is blocking your IP address.

I was trying to connect to the MQTT broker using the GO client,
broker address was given as address + port, or tcp://address:port
Example: ❌
mqtt://test.mosquitto.org
which indicates that you wish to establish an unencrypted connection.
To request MQTT over TLS use one of ssl, tls, mqtts, mqtt+ssl or tcps.
Example: ✅
mqtts://test.mosquitto.org

In my case, enable the IIS server & then restart and check again.

We are using a SpringBoot service. Our restTemplate code looks like below:
#Bean
public RestTemplate restTemplate(final RestTemplateBuilder builder) {
return builder.requestFactory(() -> {
final ConnectionPool okHttpConnectionPool =
new ConnectionPool(50, 30, TimeUnit.SECONDS);
final OkHttpClient okHttpClient =
new OkHttpClient.Builder().connectionPool(okHttpConnectionPool)
// .connectTimeout(30, TimeUnit.SECONDS)
.retryOnConnectionFailure(false).build();
return new OkHttp3ClientHttpRequestFactory(okHttpClient);
}).build();
}
All our call were failing after the ReadTimeout set for the restTemplate. We increased the time, and our issue was resolved.

This error occurred in my application with the CIP-protocol whenever I didn't Send or received data in less than 10s.
This was caused by the use of the forward open method. You can avoid this by working with an other method, or to install an update rate of less the 10s that maintain your forward-open-connection.

How to read secure web requests and process web socket requests with a single Java ServerSocket?

Intro
My code can process all bytes that are sent to a server and decide whether or not to let them go through and eventually send responses. I would like to use this to use the server as web server, web socket server and tcp server in one.
Although my code is written for Minecraft, I am not asking this on a Minecraft forum because answering this question doesn't require any prior knowledge about Minecraft or its codebase.
All you need to know about Minecraft
Minecraft is a Java game that can be played online. When it is being played online, there is a server that opens a ServerSocket and all players have their own client that opens a Socket that will communicate with the ServerSocket of the server.
Anyone can create a Minecraft server and install server-side modifications on their server (for those who know Minecraft, these are usually called plug-ins). My application is such a server-side modification. Most Minecraft servers are being hosted by Minecraft host companies. The owners of the servers have some kind of access to the part of the host computer that manages the server files.
Goal
The goal of my modification is to let the Minecraft server serve more clients than just the Minecraft clients. I would like the same server to also work as web server (for http and https requests) as well as (secure) web socket server and tcp server.
Why no multiple server sockets
The most common solution would be to just create a ServerSocket for the other server types and assign a different port to all of them. However, that is not an option in my case. Most hosts forbid you to open other ports or ask extra money for it. So I need to do it all with just the Minecraft ServerSocket.
What I achieved so far
So far, I have managed to let all bytes that are sent to the minecraft server first go through my code. My code can choose whether or not to let the bytes continue to the Minecraft server code. It can also send responses on its own without the need to inform the Minecraft server code at all.
In principle, what I have managed to do is sufficient to accomplish my goal, but I would like some help with how to continue. I will explain below what I have and have not accomplished so far.
The first byte that is sent by a Minecraft client to the server is always the same, namely 16. This is great because it allows me to easily distinguish Minecraft clients from web browsers and tcp clients.
HTTP requests and websocket connections always start with the same byte, namely 71. HTTPS and secure websockets always start with the byte 22. The TCP connections I was talking about will be sent by my own applications, so I can choose exactly what bytes they will send and I can simply program my modification to respond to that.
I managed to distinguish http requests and websocket connections by their connection property. Http requests always send 'Connection: keep-alive' while websocket connections always send 'Connection: upgrade'. (Although some browsers do the k, a and u in uppercase and others do not.)
Handling normal http requests wasn't very hard to do. Handling TCP connections won't be hard either because I will control everything. But I have issues with the remaining connection types:
Problems I need help with
The web socket protocol is quite large and I would prefer not to handle it completely with only my code. (I tried this before, but I kept having problems with the parts that were rarely used and thus not tested.) So I would like to use some library that allows me to only worry about the payload rather than the entire protocol. Unfortunately, web socket libraries generally want to create the ServerSocket, which is not possible in my case. So does anyone have advice on what to do here?
I haven't found any info on how to read https requests properly. Could someone tell me where to look for the details of this protocol or provide a nice link?
For secure web sockets, I will face the same problems as with the 'normal' web socket connections after I find out how to read the requests.
Code
All my code so far can be found at https://github.com/knokko/Multi-Purpose-Server. The most interesting part is probably the part where my code gets the opportunity to process all bytes before they arrive at the Minecraft code, that code is shown below.
Short question(s)
For those who didn't understand exactly what my question (you could see it as 2 questions that are strongly related) is:
-How I should read https requests and secure web socket handshakes?
-Does anyone know a library that can handle web socket input that doesn't require to create the ServerSocket itself?
// This channel handler will be registered for every connection client that will
// inspect
// any message before it reaches the Minecraft code.
pipeline.addFirst("multipurpose_handler_inspector", new ChannelInboundHandlerAdapter() {
private boolean deactivated;
private ChannelListener listener;
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
//super.channelRead will send the content to the minecraft code
try {
if (!deactivated) {
ByteBuf message = (ByteBuf) msg;
if (listener != null) {
listener.read(ctx, message);
} else {
byte firstByte = message.getByte(0);
// All Minecraft connections start with the byte 16
if (firstByte == 16) {
deactivated = true;
super.channelRead(ctx, msg);
}
// All insecure web connections start with the byte 71
else if (firstByte == 71) {
byte[] data = new byte[message.readableBytes()];
message.getBytes(0, data);
WebHandler.Type type = WebHandler.determineConnectionType(data);
if (type == WebHandler.Type.HTTP) {
listener = new HTTPListener();
listener.readInitial(ctx, message);
} else if (type == WebHandler.Type.WEBSOCKET) {
// TODO Find a nice way to handle web socket connections
listener = new WebSocketListener();
listener.readInitial(ctx, message);
} else {
deactivated = true;
super.channelRead(ctx, msg);
}
}
// All secure web connections start with the byte 22
else if (firstByte == 22) {
// TODO implement the secure web protocols and find a way to read this stuff
// and find the difference
System.out.println(
"We are dealing with a secure websocket or https connection");
byte[] data = new byte[message.readableBytes()];
message.getBytes(0, data);
System.out.println(new String(data));
}
// My applications
else if (firstByte == 31) {
listener = new TCPListener();
listener.readInitial(ctx, message);
} else {
System.out.println("Unknown connection type");
deactivated = true;
super.channelRead(ctx, msg);
}
}
} else {
super.channelRead(ctx, msg);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
});

If you can ALWAYS identify the Minecraft traffic, your best bet might be to run an apache/httpd and/or tomcat server on the same box and forward all non-Minecraft traffic to it. If you do this, the HTTPS stuff might just be a matter of correctly configuring the http server for https traffic.
You may have to configure your code as an http proxy--in fact (Just thought of this) you might want to go out and look for an open source http proxy and just tweak it with your code to extract Minecraft traffic and forward it before doing the rest of the proxy stuff.
I wouldn't do the HTTPs stuff from scratch, it's not terribly difficult but I'd call it non-trivial.
Oh and if your problem is "differentiating Minecraft HTTPS traffic from other HTTPS connections on the same port" I can't help except to say that this might be a good subject for your question :)

Asterisk-java. Queues action

Help me please with the question:
I need to get information about the queue (the best option would be for a particular queue and all queues). I use the asterisk-Java 2.0.3 library. For information about a particular queue, I can send the action - QueueSummaryAction. To get all the queues I can use the AsteriskServer object and get the information using getQueues(). However, this information is slightly incomplete.
In addition, I connect to the server Asterisk via telnet. And after doing the appropriate action (action: queues), I get a list of queues with pretty good information (see image).
I would like to somehow get this with the help of AMI and the implementation presented in this library. Can there be any analogy? For example, I'm interested in the number of calls, the number of responses, deductions (in image it's W:0, C:5, A:24, SL:100.0%, within 60s). But, unfortunately, I did not find a way to get such information. Part of the presented in the image, I can get, but I would like more (regarding the queue itself, not the queue members).
About my implementation.
I create a new DefaultAsteriskServer. Next, I add my listeners (I will not describe them here).
public void build(String hostname, int port, String username, String password)
{
asteriskServer = new DefaultAsteriskServer(hostname, port, username, password);
asteriskServer.initialize();
LOGGER.info("Asterisk server initialized");
}
public void addEventListener(ManagerEventListener eventListener)
{
asteriskServer.getManagerConnection().addEventListener(eventListener);
}
Actually, that's all.
Thank you all in advance for your help.

You should issue manager action "COMMAND"
In parameters you can put same request you show on your screen

How to simulate server down/available in java?

Our application has server/client side. The client supports both offline and online work mode.
So I need to test the client when server down, regain connective.
Question comes. How to simulate server down. Use codes to switch from down to ready, or from ready to down state.
Thanks in advance.
Joseph
update:
Actually, I could not extend the server interface to response the incorrect status. In my test scenario, the server is transparent. So incorrect url + port is a solution to do this.
But I could not modify the url when the session is valid. Another method is modify the hosts file to do this. I have to face the privilege issue in Windows.

Depends on what you mean by "server down". Possible options are:
Write a fake/dummy server that can return error messages corresponding to being down for test purposes.
Change the IP address of the server that your client looks for to a non-existing one so that it will think that the server is entirely down.

The basic idea is to mock the behavior of your server somehow. You could use mocking frameworks to do so.
You could also create manual mocks for testing purposes. Let the "proxy" of the server on the client implement this interface:
public interface IServer
{
bool foo();
}
You could create a "fake" implementation of that server and return whatever you'd like
public class FakeOfflineServer implements IServer
{
public bool foo()
{
// throw some exception here.
}
}
This approach allows you to fake different scenarios (no network connectivity, invalid credentials, etc.)
You could also use composition to switch from up to down in your tests:
public bool FakeServer implements IServer
{
private IServer offline = new FakeOfflineServer();
private IServer online = new Server();
public bool isUp = false;
private IServer getServer()
{
return isUp ? online : offline;
}
public bool foo()
{
return getServer().foo();
}
}

While testing server down, give any incorrect URL OR Port (Prefered). For recovery give the correct URL/Port.

This depends where you are testing. If you're unit testing, the best option is the mocking suggested by Bryan Menard.
If you're testing in an integration or production environment, You can actually cut the connection between you and the server.
Depending upon your operating system, you can do this in a number of ways.
For Windows based systems, Fiddler is fantastic. You can simulate almost anything, including delays on the requests and indeed just throwing requests away. It does not require admin access for Windows.
For linux based systems, one technique I've used in the past is to use a proxy server, or cut the port at operating system level. You can do this using iptables for instance:
To deny access to a particular port (25 in this case)
/sbin/iptables -I OUTPUT -p tcp --dest 127.0.0.1 --dport 25 -j DROP
and to allow it again:
/sbin/iptables --delete OUTPUT 1
You'll need root acces for this to work, but it does have the advantage that you don't need to touch your server or client configuration.

To emulate the server down case, you could write a ServerAlwaysDown class extending your actual server, but throwing ServerException (HTTP 500) for every connection.

If you want to be thorough use always the closest you have to a production environment for the tests, put client and servers in different machines and cut the connection, then restore it.