问题
I want to develop a FAX application.I searched on google and found some links ,applications for developing FAX apps on android.But I want to develop application using native app from android.In some sites i read free web services are available for sending/receiving fax using android mobile application.But I don't want to use Third party services due to security reasons.Was android provided any native app?otherwise please give me advise which way is better to develope application?
回答1:
The fax communication option is embedded in GSM protocol since the very beginning, it's natural by design. Is uses optional GSM data tranfer protocol for fax transmission, so it was lame to say that GSM audio quality isn't good enough.
There's no analogue demodulation when fax goes over GSM network, it converts to digital on entering provider's PBX.
Get an old good Nokia 9500 it had implemented Symbian-based fax application by default, that worked perfect on any GSM-provider. On some providers, you needed to enable an additional phone number for receiving facsimile messages, on some phones like Siemens M55 you could receive fax by clicking a menu option on any incoming call even by main cell line.
I think Google is responsible for providing users with an appropriate GSM faxing software for free, as most of the mobile manufacturers did before. Everything present on play market by search 'fax' or 'facsimile' is junk.
P.S. There is also a special protocol for fax transmission on VoIP lines, it's T.38 or G.711 pass-through; if your provider/nodes and hardware supports one of those you are lucky to send and receive faxes over internet connection as well. Eg. my own working set of hardware is Brother 9440/Planet VIP-156/sipnet.ru.
回答2:
You CAN record and play audio during a voice call on Android, I do it all the time! I record all my calls and play them back to other people whilst in a voice call, regularly. I also play people music from my phone, whilst in a call.
I don't know where you're getting your information from, maybe an old version of Android or a stock ROM from a network provider or manufacturer which have crippled the hardware in software but Android certainly DOES allow the recording and playback simultaneously during a call. Because of this I can record ANY quality I wish, from 3GP rubbish all the way up to CD quality, although there's no point on voice calls.
Because of this it is ENTIRELY possible to create a "Native FAX" application (as someone once termed it) on Android to send AND receive any FAX and keep records (files?) of such, just like any MMS, SMS, recorded phone call etc.
The only provision that would be required on top of core FAX functionality would be the ability to distinguish between voice calls and FAX data prior to picking up the call, which is currently only 100% accurate if you provide two different numbers or answer every call with software and miss voice calls (or piss people off calling your mobile who expect a human to answer).
You could get around this issue by assigning different numbers to a white-list for the FAX application to automatically answer but anyone using the same application would still have to call you first to confirm that you will let the FAX application answer the next call from them should they want to send you a fax.
It seems like a lot of messing around but I'm sure someone will implement sending and receiving any FAX from Android directly some time soon. Someone once said the "GSM modem (router)" inside mobile phones don't have the "hardware" to send and receive any FAX but we are not relying on hardware for the analogue FAX signal to be generated or decoded NOR are we using the GSM modem in DATA mode, therefore that argument is severely flawed.
We are however using the phone to transmit voice data (which happens to be carrying the analogue FAX signal generated by the software) which is in turn converted by the hardware into digital and transmitted digitally over the GSM networks. There's a huge difference in the application of technologies here, even though we are ultimately using the same "GSM modem (router) hardware" at the exit and entry point to get the job done. What happens inside the processor of the phone has absolutely nothing to do with the "GSM modem router" therefore we can essentially generate and manipulate any analogue signal sent to it before it does it's encoding.
Ok, now we have all this information out of the way, someone PLEASE develop a "Native FAX" application for Android :-)
Thanks
回答3:
If you research fax transmission protocols you will appreciate that simply recording sound is insufficient for the development of a working native fax application. Fax machines use a sound based handshaking procedure whose timing is totally reliant upon the efficent response over landlines that are switched by highly responsive systems. Check out www.spandsp.org on fax over VOIP for a detailed discussion. In any case, the reason you give for wishing to develop such an app is also flawed. Contrary to general public conceptions fax over the PSTN is NOT SECURE and can be tapped with a couple of wired clips and a laptop. If you wish to develop a secure method of transmitting data then encrypted email or instant messaging would be a simpler and more promising approach. Keep in mind that secure data transmission requires that both sender and recipient are using compatable protocols.
回答4:
You can't.
Android doesn't let you record calls and it doesn't let you play audio in the call.
Both are required for a fax application.
回答5:
Since last few years developers have started building working fax apps for Android. In the past there were not any app but since few years copmpanies have started looking in these type of app development also. Now you can easily found 15-20 working fax apps. Some of them are:
Faxfile
eFax
Genius Fax
PC-Fax.com
iFax
If you need more info about them then either navigate to play store or check out this website.
来源：https://stackoverflow.com/questions/5090522/is-there-any-native-app-for-android-fax