I am trying to send Skype messages with skype-java-api. All messages sent in this way are staying in sending state and never actually getting sent. I can see the messages but all are with loading logo beside them. However, when I sent message normally from Skype, it is getting sent.
I believe the "skype-java-api" is reaching (or has) it's end of life.
From the github page
Important: Desktop API is crippled now
As time passes, this project becomes less and less relevant due to
Desktop API discontinuation.
and even more important
According with issue #81, the chat support already stopped working.
It appears that this is what you encountered.
Related
I have a web-service on my server that pushes the xml data to the clients that are communicating to it over internet.
In these cases we have challenge to receive acknowledgement from the
client.
Specific case like, once client has received the data and before
sending the acknowledge, if the communication channel goes down.
Example:
In case of the software updates on clients over internet, how the server makes sure every thing is processed fine.
If you want to go on the "push" path, and you absolutely must know if the update was succesful, then you have to build your service and clients in such a way that you do know.
Basically what you need to do is build a small protocol so that information is transmitted no matter the failures of the communication channel. This means two things:
Your service does re-transmissions;
Your clients can deal with duplicate messages;
For example:
service pushes a message, client acknowledges => all good;
service pushes a message, the connection goes down, the message is lost. The client does not acknowledge since it never got the message => service pushes that same message once again at some later time. Now hopefully you get to case 1.
service pushes a message, client acknowledges but the connection fails and the service does not receive the acknowledge => similar to 2, so the service pushes that same message once again some later time and now the client receives the same message twice. It must ignore the second message but still needs to send an acknowledge so the service does not send it a third, forth, ... nth time;
And so on and so forth...
This is a high level description of what TCP does, for example. TCP is a reliable protocol over an unreliable network. It handles dropped packets, duplicated packets, etc.
Now, that would be pushing. A more simple alternative would be to use "pull" instead. The clients periodically pull the updates from the server. This is simpler to implement (the download is succesful if it worked, otherwise you try again later) but it's not without its gotchas, like for example:
controlling when clients start to pull data from the service. You can't just have them all update at the same time or you might overload the server. Clients should first ask the server if it's OK to update now or comme back later when the service is not so busy;
are you downloading upgrades in the background, from user devices? Data charges might apply so maybe it's better to ask the user if it wants the update now or later instead of doing it behind the scenes;
updating in the background, even if there is no problem with data charges might still consume bandwith when the client needs that bandwith for something else;
And so on and so forth...
The thing is this is a large topic, with general solutions that might not apply given particular situations. But it is not a new topic. Others have had these issues before. Consider for example Windows updates, how each PC's OS updates itself. Something similar happened a while ago when thick clients needed updates. The world moved to thin clients but now thick clients are making a comeback. Have a look at how these issues are solved, you will find usefull information online.
I do not think there is a way to do that. I believe the reason you are asking is for the following reasons:
1) If you are asking because you are sending a lot of data and your client deny receiving it, perhaps you can paginate it. That way you will know when the last page was accessed. You can even go one step further and just put very little data on your last page, that way you are sure that the last page is called.
2) If you are genuinely concerned about ensuring that they receive the entire data. How about suggest they access a 2nd web service which contains the checksum for the data, and suggest that they compare it.
Assuming that your web service is RESTful, your server should be stateless. The client should make sure it receives the data properly.
You could define a service to get the hash value of the data, followed by the request to receive the data itself. The client can check after the download whether the hash value of the downloaded data corresponds to the value received by the first call.
Amongst others, you could use MD5, SHA-1 and SHA256 in standard Java, as described in the Oracle documentation. This will calculate the hash value of the data from the server side.
Assuming you use Javascript from the client side, there are many possibilities to calculate the hash code using the same algorithms (jsSHA, for example).
I hope it helps.
I've been through different questions about this topic, however, none of them have cleared my doubts on the best approach notifying the client side of a server-client IM app.
The Problem:
The whole problem is how to notify the client application of updates. I've alread seen the following approaches:
Clients keeps checking for updates: From time to time, client app performs a check in the server to see if there are updates for that specific user;
Problem: it is not performatic at all. Suppose you have one million users and each one of them checks for new updates every second. Serve would have to deal with one million requests per second. Wont work.
Client app opens a socket: The client app opens a socket and sends its address to the server. Server, by its turn, persists this information and connects to the socket whenever it needs to notify the client of some update.
Problem: Often the client will be connected to a NAT, so, the IP it has access to is in a non-visible range. In order to send messages to this client, a port forwarding in the NAT would have to be configured, which can't be done.
Despite of the technology, I think this approach will always be used, however, I have no idea how the problem described above can be solved.
Google Cloud Message (GCM): use the GCM service to notify the client of any update. Problem: It does't seems right to use a third server to handle the IM and it raises concerns about the scalability of the system. When the number of messages and users increases exponentially, it seems that the service will go down. Despite that, it seems that passing the information for two servers before delivering to the targets just adds bottlenecks in the process.
A combination of 2 and 3: uses GCM to reach the client when the last persist addres is no longer available.
Problem: same as described in 2
XMPP: I've seen many answers indicating the use of XMPP for IM applications, however, XMPP is a protocol - as per what I've foun in the web. I don't see how it can solve the problem described in 2 for instance.
Given the options above, can someone indicate me what line should I try to go for? Which one of these approaches has the best chances of success?
Thank y'all in advanced.
Use Google Cloud Messaging. Opposing to what you stated this service is built to scale to billions of users it will generally not introduce performance bottlenecks.
What you basically want to do is to use the messaging service to wake up devices. If you insist you can then still use your client server approach and thus your own protocol to have the client lookup new messages from the backend.
I'm working on an application that handles text messages. This is a personal application and I do not plan to release it, however it's basically going to allow me to share my text messages (and phone number) between numerous devices through the internet. It's a fun learning project too as a first application, and I've done quite a lot.
However the annoying part is the text-message popup that my device gets when receiving a message. I love it when I'm using the device, and I could always just go into the options and disable the popup when I'm not planning on using the device, but I'm a very, very forgetful person and turning it back on wont always happen. Then I'll never reply to messages.
Basically I want to programmatically interrupt (or not even notify) my default messaging application of the text message, however I still want it to be logged in my messaging history. So the message can't just be "discarded". This should only happen of-course while my applications service is running.
I've been searching through the android API for quite some time and I just can't seem to figure this out, is it possible and if so can you link me to the proper place in the API to begin?
Basically I want to programmatically interrupt (or not even notify) my default messaging application of the text message...
This isn't possible.
Assuming by "interrupt" you mean to prevent the default SMS app from issuing its Notification, you can no more do this with the default app than you could with any other app that you don't control.
Additionally, as the default SMS app responds to the SMS_DELIVER_ACTION broadcast, and it is the only app to receive this broadcast, it wouldn't be possible to "not...notify" the default app of an incoming message. Your app wouldn't even have a chance to abort the broadcast, even if it were possible to do so.
(In versions prior to KitKat, it was oftentimes possible to register a Receiver with a high priority for the SMS_RECEIVED_ACTION broadcast, and then abort the broadcast before the native SMS app received it. This is what rajan ks's answer refers to.)
...however I still want it to be logged in my messaging history.
The default SMS app is responsible for writing all incoming messages to the Provider. Even if you were able to prevent the default app from receiving the incoming message, your app would then have to write the message itself. This isn't really possible, either, as the default app is the only one with standard write access to the Provider.
I currently am developing a semi-simple chat app. I want the user to be able to communicate with one other person in a private chat. Just plain text will be sent. Currently my system calls php scripts from a webpage, passes in parameters and then parses the data returned. I have it so that the client sends the message, which calls a send message script on my webserver, the script then makes a message file on the webserver and then returns a success or failure back to the client. Then for the client to view this message, it would have to call a script that checks the server for a message file with a message for him. If it finds one, it sends the message back, if not, it sends a response about not having messages.
This technique works perfectly besides the fact that the client either would have to manually refresh to check to see if he had messages, or a background thread would have to refresh every few seconds. That would be fine, however that would use data if the user was on a mobile network. Not to mention the kind of resources a background loop would pull if it was refreshing at a speed that would be convenient.
So, I decided on a second idea, this would be a server programmed in Java, which would communicate over sockets. The user would send the message as a packet over the socket and the server would check to see who it was meant to go to. If the person is online, it passes the message along to that user. However this method requires a constant connection between the client and the server and that is unreliable because what if the user is in the car and data cuts out. Or some other situation where the connection gets severed. Then it would throw errors and have to reconnect.
Anyhow, my question is which technique is better. Or are they both terrible? If so, what is the correct way of doing this? Thanks in advance.
AngularJs and Ajax will be the perfect solution for you , try to learn
for actually real time messaging Use AngularJs
If the amount of data is very less ..say 20-25 messages per day...you can REST APIs on your server to transfer actual text messages and Google Cloud messaging for pushing notifications..Recently I followed this approach to develop private chat for one of my friend.
I have a constantly-running Java program that needs to send an email whenever it encounters a problem. However it is possible that the mail server it uses could be down at the time it tries to send the email.
What is the best way to ensure that the email will be delivered when the mail server comes back up?
Queue up the requests. Have a separate thread which merely waits for something to enter the queue, then tries to email it. If it fails, it waits a few hours and tries again. Once it sends a message, it goes back to the queue to get the next message.
Put the email object into a stack or list when it fails to send, when the email server comes back up, pop each email out until it is empty.
You may want to save the email in a file, perhaps an xml file, so that should the application crash you won't lose this information.
This file is loaded when the application starts, and it keeps everything in memory, so that while there are pending emails then it keeps checking every 5 minutes or so, then, as it sends each email it will resave the xml file, so that should it crash after sending 3 emails out of 10 it won't resend those three when it starts up.
But, how you handle that is really going to depend on the specification for how to handle error conditions.
If you go from "forward everything to this SMTP server which is always there" to a situation where you need to handle all kinds of conditions normally handled by a full SMTP-server like retry later, retransmit if connection closed, use MX-hosts in their stated order and similar, you may want to consider simply having a SMTP-server inside your client (but one that does not accept incoming connections) since this moves all the dirty logic away from your applications.
I believe that the James email server - http://james.apache.org/ - is easily embeddable, but I have not actually tried.
The suggestion of using James is a good one but I've had some issues in the past of James being a bit flaky and needing to be restarted.
You could use something like Quartz to have a scheduler check for messages that need to be sent. If the message can't be sent (eg. smtp server isn't available), then that message is rescheduled to be sent at a later time. You could either have a task per message or have a persistent task that checks for messages and available mail server then sends the messages. The persistent task would give you email batching.
If you are in a Unix/Linux world, then consider the alternative of sending your alerts using syslog, and dealing with the generation of emails on that side. For example, nsyslogd has a module called ommail for generating emails natively.
IIRC, there are adapters for log4j and the like that can bridge between the Java and syslog worlds with a minimum of (zero ?) coding.
Apache James - http://james.apache.org/ will let you run your own mailserver as a proxy, not only that but is written in 100% java, so you can figure out what its doing,
and as an extra bonus James uses databases to queue the mail, so you can even inject mail directly into the queues by inserting into a database, then leave whole business of sending the mail up to James.