I've recently become interested in trying to adapt my Rock-Paper-Scissors game into a multiplayer-friendly program, so today I decided I'd look up a tutorial on servers. It seems I'm following it precisely (aside from using a different IDE). However, something is going wrong and I'm not sure exactly what it is, and it works fine for the tutorial maker. I've looked up EOFException but it didn't exactly help me out.
The tutorial on Youtube
My screenshot of the issue.
[Documentation on EOFException](I had a link here, but I need at least 10 reputation to post more than two links)
"Signals that an end of file or end of stream has been reached unexpectedly during input.
This exception is mainly used by data input streams to signal end of stream. Note that many other input operations return a special value on end of stream rather than throwing an exception."
[A similar but apparently unresolved question asked here](I had a link here too]
By the way, if you look up exactly what I've posted here, you'll also find that I've asked it at DaniWeb. I'm just posting in multiple places in case it isn't resolved at one or the other. If it is, well... the more knowledge, the better.
EOFException during readUTF() just means it's reached the end of the stream, like it says on the tin. Note that this method doesn't return null at end of stream, unlike readLine() (but like all other readXXX() methods).
It can also mean that your sending and receiving is out of sync, e.g. you are trying to read some ridiculously large number of bytes because you left out a readInt() or similar, or you wrote something extra at the peer that you shouldn't have, so you're trying to read the next bytes in the stream as the result of writeUTF() when it isn't. This is an application protocol error.
How this happened in the code you posted is another question, but your code doesn't close the sockets, which doesn't help. Add an out.close() to your server code, and in.close() to the client code. However I cannot reproduce your problem with or without these closes. Are you sure this is the real code?
Related
I want to fetch data from two API requests parallelly.
Single<TodayDataEntry> todayDataEntrySingle = openWeatherApi.getTodayData(
"London,uk", FetchDataUtil.API_KEY).subscribeOn(Schedulers.io());
Single<ListWrapper<ForecastDataEntry>> forecastDataEntrySingle = openWeatherApi.getForecastData(
"London,uk", FetchDataUtil.API_KEY).subscribeOn(Schedulers.io());
Single<DataAll> observable = Single.zip(
todayDataEntrySingle,
forecastDataEntrySingle,(t1, t2) -> {
return new DataAll(t2.getList(), t1);
}).subscribeOn(Schedulers.io());
After subscribing, if both API requests fail (like in case where there is no internet connection), one of the error signals is not handled (even though onError is getting called), causing app to crash.
However if I use Observable<> instead of Single<>, the error is handled
and an exception is not thrown. Is something wrong in my
implementation?
If I don't call subscribeOn(Schedulers.io) for individual observables and instead just call for zipped one, the exception is not thrown. However as far as I know, in this case the API requests are not in parallel.
We were facing the exact same issue with Completable.mergeArray() and it literally took us years to figure this out. In summary, the crash is caused by the streams running in parallel and throwing an error at the same time.
We wrote an extensive blog post series describing the issue and our workaround. I think it'll definitely help if you take a look. Let me know in the comments if you have any questions.
I have a question about inner Matlab error management. Right now I have quite a large program with a lot of variables and functions that cumulated over my code writting and I'm 100 percent sure that I did not catch all the bugs and mistakes in the program and I don't want it to crash completely when is used by layman user. So, is there a way to display errordlg message and for example restart the program when there will be any given error directly by Matlab (for example when I forgot to declare a global variable etc.)?
Thanks for answers, Peter
Crashes are good, because they force users to report bugs.
If you don't want to go that route, Matlab provides try-catch: wrap your code in a try-catch block. If there is an error, you'll find yourself in the catch block where you can have Matlab send you an email with the error message, and restart the program if necessary.
You can use try/catch statements to respond to errors in your program. There's more information here.
I'm fairly new to using Google Docs, but I have come to really appreciate it. The scripting is pretty easy to accomplish simple tasks, but I have come to realize a potential speed issue that is a little frustrating.
I've got a sheet that I use for my business to calculate the cost of certain materials on a jobsite. It works great, but was a little tedious to clear between jobs so I wrote a simple script to clear the ranges (defined by me and referenced by name) that I needed emptied.
Once again, worked great. The only problem with it is that clearing a few ranges (seven) ends up taking about ten full seconds. I -believe- that this is because the spreadsheet is being saved after each range is cleared, which becomes time intensive.
What I'd like to do is test this theory by disabling autosave in the script, and then re enabling it after the ranges have been cleared. I don't know if this is even possible because I haven't seen a function in the API to do it, but if it is I'd love to know about it.
Edit: this is the function I'm using as it stands. I've tried rewriting it a couple of times to be more concise and less API call intensive, but so far I haven't had any luck in reducing the time it takes to process the calls.
function clearSheet() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
sheet.getRange("client").clear();
sheet.getRange("lm_group_1").clear({contentsOnly:true});
sheet.getRange("lm_group_2").clear({contentsOnly:true});
sheet.getRange("dr_group_1").clear({contentsOnly:true});
sheet.getRange("dr_group_2").clear({contentsOnly:true});
sheet.getRange("fr_group_1").clear({contentsOnly:true});
sheet.getRange("fr_group_2").clear({contentsOnly:true});
sheet.getRange("gr_group_1").clear({contentsOnly:true});
sheet.getRange("client_name").activate();
}
That is not possible, and will probably never be. It's not "the nature" for Google Docs.
But depending on how you wrote your script, it's probable that all changes are already being wrote at once, in the end. There's some API calls that may be forcing a flush of your writings to the spreadsheet (like trying to read after you wrote something), but we'd need to see your code to check that.
Anyway, you can always check the spreadsheet revision history to verify if it's being done at once or in multiple steps.
About the performance, Apps Scripts have a natural delay that is unavoidable, but it's not 10s, so there's probably room to improve on your script, using fewer API calls and preferring batch calls like setValues over setValue and so on. But then again, we'd have to see your code to assert that and give more helpful tips.
Okay, I just started learning golang and I like it so far. However I don't find their documentation good for go starters, Here is my problem.
I wanted to write little server program that accepts connections and writes something to the client. No problem doing that so far.
However as soon as the thing get a real functionality, I need to be able to handle multiple clients, which I though would also be a good exercise for goroutines.
listener, error := net.Listen("tcp", remote)
con, error := listener.Accept()
go handleClient(&con);
func handleClient(con *net.Conn) {
I've cut most of the code out. The problem is, no matter what I try, I can't pass con.
con.RemoteAddr undefined (type *net.Conn has no field or method RemoteAddr)
(found that in this example: http://raycompstuff.blogspot.com/2009/12/simpler-chat-server-and-client-in.html).
So i tried looking at the documentation, but it just gave me the source of the net package.
Read trough the source, and figured it should be
undefined: TCPConn
How can I pass the connection of a client to a goroutine, so i can handle multiple clients at once?
Ok, figured it out.
There is some guy who actually already wrote what I wanted to write in go.
https://github.com/dustin/gomemcached/blob/master/mc_conn_handler.go
go handleClient(con);
func handleClient(con net.Conn) {
It seems that since boost 1.40.0 there has been a change to the way that the the async_read_some() call works.
Previously, you could pass in a null_buffer and you would get a callback when there was data to read, but without the framework reading the data into any buffer (because there wasn't one!). This basically allowed you to write code that acted like a select() call, where you would be told when your socket had some data on it.
In the new code the behaviour has been changed to work in the following way:
If the total size of all buffers in the sequence mb is 0, the asynchronous read operation shall complete immediately and pass 0 as the argument to the handler that specifies the number of bytes read.
This means that my old (and incidentally, the method shown in this official example) way of detecting data on the socket no longer works. The problem for me is that I need a way detecting this because I've layered my own streaming classes on-top of the asio socket streams and as such, I cannot just read data off the sockets that my streams will expect to be there. The only workaround I can think of right now is to read a single byte, store it and when my stream classes then request some bytes, return that byte if one is set: not pretty.
Does anyone know of a better way to implement this kind of behaviour under the latest boost.asio code?
My quick test with an official example with boost-1.41 works... So I think it still should work (if you use null_buffers)