Can any one tell me which is more stable? I know each has their own advantages and disadvantages. But which one is better for http, etc?
In my previous application I used indy9 but I wasn't satisfied with it, as I would sometimes get strange errors.
Can anyone recommend one?
I use Indy in a lot of projects. I used both 9 and 10 mainly as HTTP server and proxy. The projects get very intense traffic at times (HTTP). Indy never did let me down. It works very stable.
But I also had some "strange" situations where I had to dig deep to find the underlying problem. I also do not like the way Indy tends to handle a lot of things through exceptions. In general I like the ICS coding style more. But let me go to ICS.
ICS uses non-blocking sockets, while indy uses blocking. While non-blocking is ok and seems to be better at first sight, I found it irritating in a lot of situations. The problem is that the natural flow of the code gets lost because of the callback functions. This makes it harder to write procedural type of libraries. Furthermore I do not like how everything is handled through messages. For me it gets messy real quick when mixed with multithreading. And multithreading is mainstream these days.
So while I like the coding style and quality of the code in ICS, I prefer the simplicity of use and blocking mode of Indy. What you like more is up to you, but both libraries are mature and stable.
These are my two cents.
I also use both Indy and ICS.
Most of the time I prefer Indy because implementing sequential type of protocols with it is very easy (the request runs in it's own thread so you simply Read/Write to the connection, really easy). Using Indy requires solid knowledge of threading and synchronization. Unlike Runner I like how Indy uses Exceptions to handle "exceptional" stuff because it allows me to concentrate on the normal flow of the protocol (I use try-finally blocks to make sure I deallocate resources).
I also used ICS in a application where Indy simply failed: I used it for an application that implements an TCP/IP proxy. Using ICS was simpler because of it's non-blocking nature. I was able to "proxy" TCP/IP protocols that I know nothing about, so I have no idea how bytes would flow from one end to the other. Indy failed in that scenario because in Indy you're ether reading or you're writing, you can't do both at the same time. Using ICS to implement an sequential-type protocol is a bit of pain: you essentially need to use state-machine logic, brake the protocol in small bits, keep flags laying around so you know where you are in the protocol. An big plus: François Piette, the author of ICS, is active and very helpful on a number of forums and mailing list, and is very prompt to help with anything related to ICS.
For me, if I need to do something with TCP/IP, the decision path is very simple: Can it be done with Indy? Then it's Indy. If it can't be done with Indy then it'll be done with ICS!
I've used Indy 9 and 10 for TCP, HTTP and FTP with very few problems. ICS is a good choice, too. It's non blocking, which will change how you use it.
I haven't used it, but I've heard good things about Synapse, which is also blocking.
We test Indy10 IdTCPClient to receive video stream from remote server, it's OK. But when it's receiveing stream, the same time use it send some data to the server, after some minute, the received stream data began lost data bytes. We use sniffer tool to trace this problem, confirmed that IdTCPClient lost some bytes in receiveing stream.
So, we test Indy9.018, the same problem happend but a few times VS. Indy 10.
Remember that Indy is always in beta stage. Sometimes you need to work with night builds.
Which one is better really depends on specific use case, but I was unhappy with indy as an http client and ICS ended up being exactly what I needed it to be, with a lot less random quirks.
Note though that it is non blocking, so it's not just a drop in replacement.
I use Indy 9 for stable, released, production code to over 1 million users, and have never received any strange errors.
I'd say the answer depends on what you want to do with the internet. Indy is fine if you are prepared to get involved with understanding how it works, and is very capable. ICS is a different take on things, and I've used it effectively for many-connection systems. But for day to day "grab a file or send an email" type stuff, where you want to do a basic task, I pretty much always use Clever Components Internet Suite as you just create the component,
set the options, and it works. The suite is quite comprehensive, and gets useful updates.
Related
I want write a program in Delphi to watch the internet connection, and if a certain response received (in response to request from a program), send request again encoded to another server, get a new encoded response, decode it, and pass it as response to the program who sent the main request. But I don't now how to hook internet connection. I want to use this program to pass through filter my country governments made using a private program to avoid blocking it. Is there any idea?
Thanks for your answer.
Magenta Systems released a free set of Delphi components that let you see the network traffic on your computer and examine the content. If you see the response you are looking for, your monitoring program can send a request to another server.
Off the top of my head, I'm not sure if it will let you alter the content of the original packet. If not, then Marcus' suggestion of using a proxy might suit you better.
You can either try to hook stuff at the Winsock level (there's plenty of examples for that around), but I suggest you go one level deeper and use a Layered Service provider (LSP).
I have used Komodia's redirector from http://www.komodia.com. Commercial, but well worth it.
See also this post
Is it possible to intercept dns queries using LSP/SPI?
I want to download a file from internet and I imagine this should be a simple task. Trying several different approaches I have found that each one has its own drawback.
The main issues are:
Application freezes until it downloads the file
Application freezes forever if the Internet connection is lost/server does not respond.
(details:
How to retrieve a file from Internet via HTTP?
The connection does not timeout while downloading file from internet )
So, finally I used the suggestions I got from several people to use "pro" libraries such as Indy. However, Indy is not much better than the pieces of code I have tried (but it is way much larger and difficult to maintain). While using Indy the application does not freezes only for short periods so it is still (somehow) usable. However, the application cannot be shut down until the download finishes (never if the Internet connections gets broken).
Other people reported the same problem: http://borland.newsgroups.archived.at/public.delphi.internet.winsock/200609/0609079112.html
https://forums.embarcadero.com/thread.jspa?threadID=25199&tstart=90
So, there is some hacking I had to do to TIDAntiFreeze in order to make it work?
Also, the ConnectTimeout property is not recognized.
fIDHTTP := TIDHTTP.Create(NIL);
fIDHTTP.ConnectTimeout:=5000;
Should I drop Indy and return to original idea of downloading the file in a separate thread and end the thread when it does not respond (at least this way I get rid of 3rd party libraries)? There will be unforeseen side effects if I do this?
Using: Delphi 7, Indy 10.1.5 10.5 (probably).
Thanks
You probably need to use Indy the Indy way: using threads. Indy was specifically designed to work in blocking mode, because that's how most internet protocols work (example: with HTTP, at protocol level, you send a request, then you read the response. You don't send and receive at the same time). TIdAntiFreeze is supposed to help you use some Indy functionality without dealing with threads; I never used that because, at least conceptually, it's an ugly hack.
If you don't want to deal with threads then you should take a look at ICS - it was designed to be used in async mode, without threading. It doesn't need the equivalent of TIdAntiFreeze because it's not blocking. You start a download and you handle some events to get progress and completion notifications. ICS is just as well-known, professional and wildly used as Indy.
It's not too difficult to solve these sorts of problems. The first thing you have to do is make sure that you have properly handled error handling. If something fails then make sure everything cleans up properly. Beyond that make sure the downloading code is part of a separate thread. If there is any problem you can always terminate the thread from your main program. Here's the code (for downloading only, not the threading) which is working fine for me.
with TDownloadURL.Create(nil) do
try
URL := 'myurltodownload.com';
filename := 'locationtosaveto';
try
ExecuteTarget(nil);
except
result := false;
end;
if not FileExists(filename) then
result := false;
finally
clear;
free;
end;
We have a requirement from a customer to provide a "lite" version for dial-up and all the bells-and-whistles for a broadband user.
The solution will use Flex / Flash / Java EJB and some jsp.
Is there a way for the web server to distinguish between the two?
You don't care about the user's connection type, you care about the download speed.
Have a tiny flash app that downloads the rest the of the flash, and times how long it takes. Or an HTML page that times how long an Ajax download takes.
If the download of the rich-featured app takes too long, have the initially downloaded stub page/flash redirect to the slow download page (or download the bare-bones flash app, or whatever).
The simplest and most reliable mechanism is probably to get the user to select their connection type from a drop down. Simple, I know, but it may save you a world of grief!
There's no way to distinguish between a broadband or dial-up as a connection type, but you can make an educated guess by connection speed.
Gmail does this and provides a link to a basic HTML version of their service if they detect it.
(source: nirmaltv.com)
My guess is that there is some client side javascript polling done on AJAX requests. If the turnaround time surpasses a threshold, the option to switch to "lite" appears.
The best part about this option is that you allow the user to choose if they want to use the lite version instead of forcing them.
Here's a short code snippet from a code who attempted something similar. It's in C#, but it's pretty short and it's just the concept that's of interest.
Determine the Connection Speed of your client
Of course, they could be a temporary speed problem that has nothing to do with the user's connection at the time you test, etc, etc.
I had a similar problem a couple of years ago and just let the user choose between the hi and lo bandwidth sites. The very first thing I loaded on the page was this option, so they could move on quickly.
I think the typical approach to this is just to ask the user. If you don't feel confidant that your users will provide an accurate answer, I suspect you'll have to write an application that runs a speed test on the client. Typically these record how long it takes the client to receive x number of bytes, and use that to determine bandwidth.
Actionscript 3 has a library to help you with this task, but I believe it requires you to deploy your flex/flash app on Flash Media Server. See ActionScript 3.0 native bandwidth detection for details.
#Apphacker (I'd comment instead of answering if I had enough reputation...):
Can't guarantee the reverse, either--I have Earthlink dial-up, soon to upgrade to Earthlink DSL (it's what's available here...).
You could check their IP and see if it resolves to/is assigned to a dial up provider, such as AOL, Earthlink, NetZero. Wouldn't guarantee that those that don't resolve to such a provider are broadband users.
you could ...
ask the user
perform a speed test and ask the user if the result you found is correct
perform a speed test and hope that the result found is correct
I think a speed test should be enough.
If you only have a small well known user group it is sometimes possible to determine the connection speed by the ip. (Some providers assign different subnets to dial-up/broadband connections)
I have a simple application, which should send a single byte to a serial port once a minute. But sometimes, from some strange reason, it freezes somewhere in the WriteFile() function. Both sw and hw flow controls are turned off. I've googled some stuff about pending read operations performed from another threads, but I believe this is not a problem, because my app has single thread. Also, handle from CreateFile looks valid, so the port should not be used by any other applications. Have anybody suffered this?
If you google for the words writefile hangs, you'll find a number of discussions on this problem. Some leads are buffer overruns, sizing your buffer correctly, a defective COM port, clearing the status on error... Seems like there are plenty of things to try.
Another thing I would suggest is to use a communications library instead of calling the API directly, something like Async Professional (http://sourceforge.net/projects/tpapro/). Even if they add some overhead to your application, they might simplify your work and avoid a number of potential pitfalls...
Well, I'm using this library: http://lhdelphi.ic.cz/uploader/storage/ComDrv32.pas in Delphi 7, on Windows XP, but the component inside is just a wrapper around some Win API calls, CreateFile, WriteFile, etc.
Have you tried setting CommPortDriver.CheckLineStatus to true ("to prevent hangs when not device connected or device is OFF")? The source for the comdrv32.pas library contains that suggestion.
You can also try ComPort, which was neglected for some time but is now actively developed again.
We're working on an application that displays information through a Direct3D visualisation. A late client request is the ability to view this application via some Remote Desktop solution.
Has anyone done anything similar? What options are available / unavailable? I'm thinking RDC, VNC, Citrix...
Any advice?
I think you can still use all of the normal D3D tools, but you won't be able to render to a surface associated with the screen. You'll have to render to a DIB (or some such) and Blt it with GDI to a normal window HDC. RDC/VNC/Citrix should all work with this technique.
Performance will definitely suffer - but that's going to be the case over remote desktop anyway. In fact, if I were you, I would mock up a VERY simple prototype and demonstrate the performance before committing to it.
Good luck!
I think Windows 7 has D3D remoting stuff - probably requires both client and server to be W7 though.
The build-in remote desktop works. (You don't have to do anything special)
But it is extremely slow, because when in doubt, it just sends the contents of a window as a bitmap.