I've been wanting to make an app that sends instructions over serial to my LED controller. For this to work, I need to read what the controller sends back after sending it a command. I found the following function in ORSSerialPort:
func serialPort(_ serialPort: ORSSerialPort, didReceive data: Data) {
// Do things
}
However, is there something like ORSSerialPort.read()?
I don't think ORSSerialPort.read() is a good idea. I know some other serial libraries are written that way, but the only way for that to work is for read() to block (possibly with a timeout) until a byte comes in on the port. Blocking I/O makes it a lot harder to write a good, responsive app, and I want to guide developers using ORSSerialPort away from that approach.
Instead, you should indeed implement serialPort(_:, didReceive:) in your ORSSerialPort delegate. When data is received by the serial port, that method will be called with the received data and you can do whatever you'd like with it.
That said, if your device communicates using a command/response type protocol (ie. every time you send a command, the device sends some response), you ought to look at ORSSerialPort's request/response API. It allows you to explicitly define the format of expected responses to commands, and ORSSerialPort itself will handle asynchronously waiting for, parsing, and validating responses. See the documentation for more info about this part of ORSSerialPort. The library also includes a sample project, RequestResponseDemo, that demonstrates using this API. Both Swift and Objective-C versions are included.
The ORSSerialPort library is popular and generally good. However, I'd found that it didn't work well with TTY serial devices. This was primarily because of its use of IOKit to discover serial ports -- it would only discover physical devices.
This is likely OK in your case but where you want to test your code but don't want to connect to a physical device, it falls over. Good code always needs a testing framwork. So, check out https://github.com/kpishere/POSIXSerialPort for a very simple serial interface API it is just what you need to write and respond to incoming data and also works with physical or virtual devices (as Unix was originally envisoned!).
To your question though, you don't want to call read() directly. You get into understanding whether or not, "is it a blocking read?" Then you get into dealing with threads. Both of the suggested APIs insulate you from that and allow you to think in terms of an event driven model -- this makes for much simpler code.
Related
While using tshark, I want to capture a packet that contains a specific string.
After executing tshark, I want it to stop receiving packets immediately when it receives a packet that contains the specific string and return it.
What parameters should I use to do this operation?
I think you're looking for something like trigcap, which is part of the Wireshark project, but not currently being shipped to my knowledge because it apparently doesn't work on Windows and may have problems on other platforms now too since it hasn't seen any active development in quite a long time AFAIK.
You can try to compile it yourself to see if it meets your needs. Read more about it at:
Bug 2039 - Triggered Capture
what is the work of trigcap?
If you're on Windows, you might want to take a look at the dumpcap.bat file posted on the Wireshark wiki Tools page.
All of these solutions rely on BPF (pcap-filters), so whatever string you're looking for as your stop condition needs to somehow be manipulated into that format, which may not be easy to do.
I need help, I'm desperate
During two weeks I have been working in my project, this uses serial port communication (a PIC serial board). I got to set the connection up, but I can not get data from the COM port. I've read some forums and the cause of the problem seems to be the incomplete implementation of System.IO.Ports class.
When I try to get data of the COM port, the event SerialDataReceivedEventHandler (represents the method that will handle the DataReceived event of a SerialPort object.) is not called or activated. I tried to resolve it but I don't find a definitive solution. I thought to prove a external DLL, but a friend told me that the problem will go on, in fact I did it and got the same problem: SerialDataReceivedEventHandler does not work. Also, someone recommended me using a secondary thread, although I don´t understand how to do it at all.
I wrote a program in visual C# and everything works fine. I'm intrigued.
I need to find a solution, some idea or good documentation. If there's someone knows something about it, help me please.
I need to understand the cause of this to continue.
Unity is based on Mono, and Mono doesn't implement completely the Serial class, in particular there are no notifications implemented (such as SerialDataReceivedEvent).
That's why it works in Visual Studio, and not in Unity.
Here are the differences between the Mono and complete .NET implementation of the Serial class :
Extract from http://www.mono-project.com/archived/howtosystemioports/#limitations
"Limitations
At the time of this writing, there are a a few limitations that one must take note:
1) There is no event notification for received serial data. If you want to receive data, one must set a timeout and watch for received data by polling ReadByte() when you think there might be data.
2) One must Read data in byte[] format only – there is no char[] support. You must do your own reading of bytes and translate that into your encoding.
3) DiscardNull, ParityReplace, ReceivedBytesThreshold are not implemented."
I think it happens because the Unity is based on Mono instead of .Net, and a pretty old version of it. You couldn't use Linq on iOS devices for a long time because of AOT bugs, and the localisation implementation is buggy (or at least it was in the previous versions of Unity I tried to work with). I wasn't even able to find the source of System.IO.Ports in the source of Unity's Mono fork, so it's surprising it compiles at all.
For a toy project I want to find out if a mobile phone is connected to gsm or not. So I thought "Okay, let's use my local sip provider and see".
But in both cases, the thing goes like this:
I send an INVITE
0 s: I get a 100 Trying
5 s: I get a 183 Session description
I get an audio stream, in the one case with the ringing, in the other case with a "The person you are calling is…"
If I wait long enough (~ 40 s), I get a more appropiate status code like 180 Ringing.
Audio analysis is not an option, really.
Any hints on where to go now?
(I used twinkle for testing and a local german sip-provider.)
This issue is endemic in the way telephone networks work, and is not specific to SIP or IP. It's why, when you place a call to another country and the number is busy, you might sometimes hear your local country's busy tone, or you might hear a different busy tone that comes from the other country. In the latter case you cannot detect except by audio analysis, what the problem is. In SS7 and ISDN we speak of Q.931 cause codes instead of SIP error codes, but the principle is the same.
There's an argument to be made for configuring telephone systems to emit status codes instead of audio error messages. For callers using normal phones, the originating switch (the one closest to the caller) can then map that code to the appropriate spoken error message or audio tone. That way, when the call is being placed by software rather than by a person, the software can have access to the actual error code right away.
On the other hand you can also argue for having the remote switch (the one nearest the destination or the one that encounters the problem) speak its own error message. That switch knows best what the actual problem is. For example, a mobile operator can emit a spoken error message saying that the mobile phone you are trying to call is currently out of range. There is no Q.931 code (or SIP error code for that matter) with that meaning. It could return 27=Destination out of order?? Or 35=Destination unattainable?? Both of those codes are so esoteric, who knows what error message the local switch would translate them to (in practice: probably just a reorder tone, which is really user-unfriendly to a human caller). And when you try to map Q.931 cause codes to SIP error codes back and forth, even more information is lost because the codes really don't match up well at all. It's likely to be a much better user experience for the caller if the remote switch just plays back an informative, appropriate, recording which describes the problem.
Since there is this dilemma (arguments on both sides), we can conclude that this will not likely be resolved by completely standardizing on one way or ther other way anytime soon.
Anyway, sometimes this is configurable: your SIP provider may be able to configure your trunk for coded errors instead of recorded messages. If they offer this (some do), it's worth a try to set this option. But results will vary: this option only affects its local behaviour. In general if you want immediately call clearing with cause code and are instead getting a recorded error message from the other end, you will not be able to do anything about it, because the switch that makes the decision on which way it's going to respond is the remote one.
When using the audio message method, a proper Q.931 cause code or SIP error code usually comes eventually (after the recording is finished), but as you point out, it's probably too late by then.
Okay, I managed to create a match between two players. Now I will do a little test about sending data to a player.
I didn't quite get the explanation about NSData. Essentially, what is it? How do I send a, dunno, array to another player?
Apple mentioned data packets could be lost. But there was a "reliable" mode to prevent that. But I couldn't find about such.
Any ideas?
Yes, you have to make your OWN protocol. "making a protocol" is something you do yourself. Something like...Essentially on the server end
// the message arrives and you then do this...
[data getBytes:&getMe length:sizeof(CommsProt)];
whereas on the client end to send messages, you do this...
NSData * data = [NSData dataWithBytes:&sendMe length:sizeof(CommsProt)];
// ...now send that data using GameKit or whatever system you end up with
and you define your protocol - at least the chunks of data - like this:
typedef struct _CommsProt
{
BOOL happyThing;
someThings wotJustHappened;
float happyValue;
float anotherHappyValue;
// etc
}
CommsProt;
If you are new to GK, be aware of this critical tip ...
Client/Server GKSessions
This could also help...
Most effective way to do networking on Mac/iPhone?
Some helpful notes...
(i) "client" and "server" mean nothing. You will be able to send the handbags of information (such as "CommsProt" above) in either direction. If you want to think of, and refer to one, end as a server (particularly if you have a hub-type arrangement), that's fine. But it's only in your head. (By the way, commonly you might use a different data structure in each direction, that's perfectly fine.)
(ii) Regarding sockets. If you get heavily in to networking, you will have to deal with sockets and write your own sockets code. However it is very likely you can choose a networking layer where you never even have to say the word "sockets"! GameKit + Bonjour, for example, completely take care of handling sockets for you, AND that combination takes care of the other incredibly difficult issue which is FINDING one of your client/servers. If you are new I recommend you completely set aside sockets for now, and use a system such as GameKit (or whatever is equivalent on Windows) for your networking layer.
(iii) Indeed AT FIRST just use something incredibly simple like GameKit, while you figure out your protocol and all the other headaches. Later, if necessary you can rewrite the networking layer, or, switch to some other package that you hear about. Happily everything up to the code examples above will be unchanged, only the networking layer will change.
(iv) Regarding WiFi. GameKit and most convenience packages, are completely agnostic to the physical layer: they take care of it for you. GK will work fine however the phones are connected -- bluetooth, ethernet, whatever! Indeed you "won't know" what physical layer is being used. (It's sometimes annoying you can't control this: let it go, users couldn't care less.)
I am currently trying to build a (simplified) stock app (like the one built-in on the iphone). I setup a simple server with a REST-interface which my app can communicate with.
However I am struggling to find the right/best way to build this kind of (streaming data consumer) client on the iphone.
My best bet at the moment is to use a timer to regularly pull the xml payload from the server (the connection is async but the xml parsing is not therefor the interface is blocked sometimes. I am a bit shy of thread programming since I learned some lessons the hard way on other platforms).
I read about websockets but it is not clear for me if and how they are supported on the iphone.
How would you do it?
Any hint would be appreciated, Thanks.
websockets aren't going to help you -- that's a server-side technology to make a socket-like interface work over HTTP.
If you don't want to block the GUI, you need to use another thread. You are right to be scared of doing this, so share as little as possible (preferably nothing) between the two threads. Use a message passing mechanism to get information from the background thread to the UI thread.
Take a look at ActorKit: http://landonf.bikemonkey.org/code/iphone/ActorKit_Async_Messaging.20081203.html
Take a look at this question.
It talks about asynchronous vs synchronous connections. You will want to use an asynchronous call to get your data so you don't lock up your UI. You could use that in conjunction with a polling timer to get your data from the server.
You can find more info about the NSURLConnection in apple's documentation here