Hi,

Do you know of an app, to be installed on an Android phone, that can
receive some kind of notification or ping from a Linux computer, in the
same LAN, from a script?

Like for telling me some job ended, whatever. Not internet, the LAN is
sufficient.

--
Cheers, Carlos.

On Mon, 27 Mar 2023 14:53:18 +0200, Carlos E.R. wrote:

> Hi,
>
> Do you know of an app, to be installed on an Android phone, that can
> receive some kind of notification or ping from a Linux computer, in the
> same LAN, from a script?
>
> Like for telling me some job ended, whatever. Not internet, the LAN is
> sufficient.

I have not tried this myself, but you might try "gotify", or one of the
other "push notification" apps available for android. You can get "gotify"
from either the Fdroid app repository, or directly from gotify.net. You
would need the "gotify server", which you can also get (as open source)
from gotify.net.

As for other "push notification" apps, I have seen an MQTT client app
for android (again, look for it in Fdroid, or Google Play), which you
can push messages to from an MQTT service (I use Eclipse Mosquitto) on
your systems. There are other push notify apps available, but most
require access through external servers, while the MQTT service and
"gotify" both can run from and on your LAN.

HTH
--
Lew Pitcher
"In Skills We Trust"

On Mon, 27 Mar 2023 14:53:18 +0200, Carlos E.R. wrote:
>
> Do you know of an app, to be installed on an Android phone, that can
> receive some kind of notification or ping from a Linux computer, in
> the same LAN, from a script?
>
> Like for telling me some job ended, whatever. Not internet, the LAN is
> sufficient.

No. But if your mail app on the phone sends audible notifications when a
new mail arrives, you could have Linux send a mail to the email address
on your phone.
--
Andreas

On 2023-03-27 20:13, Lew Pitcher wrote:
> On Mon, 27 Mar 2023 14:53:18 +0200, Carlos E.R. wrote:
>
>> Hi,
>>
>> Do you know of an app, to be installed on an Android phone, that can
>> receive some kind of notification or ping from a Linux computer, in the
>> same LAN, from a script?
>>
>> Like for telling me some job ended, whatever. Not internet, the LAN is
>> sufficient.
>
> I have not tried this myself, but you might try "gotify", or one of the
> other "push notification" apps available for android. You can get "gotify"
> from either the Fdroid app repository, or directly from gotify.net. You
> would need the "gotify server", which you can also get (as open source)
> from gotify.net.
>
> As for other "push notification" apps, I have seen an MQTT client app
> for android (again, look for it in Fdroid, or Google Play), which you
> can push messages to from an MQTT service (I use Eclipse Mosquitto) on
> your systems. There are other push notify apps available, but most
> require access through external servers, while the MQTT service and
> "gotify" both can run from and on your LAN.

Thanks.

I also got a suggestion to try <https://ntfy.sh/>, which seems very
simple. With an external server, but very simple.

--
Cheers, Carlos.

On 2023-03-27 23:08, Andreas Kohlbach wrote:
> On Mon, 27 Mar 2023 14:53:18 +0200, Carlos E.R. wrote:
>>
>> Do you know of an app, to be installed on an Android phone, that can
>> receive some kind of notification or ping from a Linux computer, in
>> the same LAN, from a script?
>>
>> Like for telling me some job ended, whatever. Not internet, the LAN is
>> sufficient.
>
> No. But if your mail app on the phone sends audible notifications when a
> new mail arrives, you could have Linux send a mail to the email address
> on your phone.

That's what I'm doing, but I get no beep, maybe I disabled it but have
forgotten.

--
Cheers, Carlos.

Carlos E.R. <robin_lis...@es.invalid> [CE]:
CE> Do you know of an app, to be installed on an Android phone, that
CE> can receive some kind of notification or ping from a Linux computer,
CE> in the same LAN, from a script?

Another option: install a VoIP client on the phone and call directly its
LAN IP address from the linux computer using a command line VoIP program
(like 'pjsua' or 'linphonec').

If you go this route, you could even send prerecorded sound files
to the phone! You can think of this setup as a reverse answering
machine...

Carlos E.R. <robin_lis...@es.invalid> [CE]:
CE> Do you know of an app, to be installed on an Android phone, that
CE> can receive some kind of notification or ping from a Linux computer,
CE> in the same LAN, from a script?

If the phone is jail-broken and you can run shell scripts on it,
a quick one-liner
while :; do wget ... && beep; sleep 5; done
should be all you need.

If it's not, there are several options depending on whether the
phone can talk to the net or not.

No internet? Use any regular SMTP client:

- Run a minimal SMTP server on another LAN box

- Configure the phone e-mail client to check for new messages on
the LAN SMTP server every N minutes

- Send messages to the phone using the LAN SMTP server

If the phone is connected to the internet already, skip the
LAN SMTP server.

If the phone is connected to the internet and no SMTP client is
installed, install a chat application which has a public API
(e.g. https://chatwork.com) and send (encrypted) messages from
the linux box to the phone using the API.

Or, if you want to go full hard-core, check out the X10 home automation
apps, after installing some compatible hub server on a LAN box.

On Tue, 28 Mar 2023 03:26:57 +0200, Fritz Wuehler wrote:

> Carlos E.R. <robin_lis...@es.invalid> [CE]:
> CE> Do you know of an app, to be installed on an Android phone, that
> CE> can receive some kind of notification or ping from a Linux computer,
> CE> in the same LAN, from a script?
>
>
> If the phone is jail-broken and you can run shell scripts on it,
> a quick one-liner
> while :; do wget ... && beep; sleep 5; done
> should be all you need.

That sounds backwards.

I was going to suggest trying making a simple, one line, server with nc
under termux, but netcat wouldn't install for me. YMMV

On 27/03/2023 23:37, Fritz Wuehler wrote:
> Carlos E.R. <robin_lis...@es.invalid> [CE]:
> CE> Do you know of an app, to be installed on an Android phone, that
> CE> can receive some kind of notification or ping from a Linux computer,
> CE> in the same LAN, from a script?
>
> Another option: install a VoIP client on the phone and call directly its
> LAN IP address from the linux computer using a command line VoIP program
> (like 'pjsua' or 'linphonec').
>
> If you go this route, you could even send prerecorded sound files
> to the phone! You can think of this setup as a reverse answering
> machine...
>

Android VOIP clients were always a bit crap, precisely because they
lacked a reliable push notification.

Obviously it is easy enough to use a busy loop, continual checking of a
remote site, but that drains the battery. The ideal would be to have an
OS observable mechanism to receive a remote push notification and wake a
local app from sleep.

I haven't checked recently to see if this has been delivered.

On 2023-03-28 03:26, Fritz Wuehler wrote:
> Carlos E.R. <robin_lis...@es.invalid> [CE]:
> CE> Do you know of an app, to be installed on an Android phone, that
> CE> can receive some kind of notification or ping from a Linux computer,
> CE> in the same LAN, from a script?
>
>
> If the phone is jail-broken and you can run shell scripts on it,
> a quick one-liner
> while :; do wget ... && beep; sleep 5; done
> should be all you need.

Nope, not the case.

And I fear it would waste the battery.

> If it's not, there are several options depending on whether the
> phone can talk to the net or not.
>
>
> No internet? Use any regular SMTP client:
>
> - Run a minimal SMTP server on another LAN box
>
> - Configure the phone e-mail client to check for new messages on
> the LAN SMTP server every N minutes

I have that, but not disimilar from using gmail. Another client wastes
battery (K9 did, which is why I don't have it checking for email except
on demand).

>
> - Send messages to the phone using the LAN SMTP server
>
>
> If the phone is connected to the internet already, skip the
> LAN SMTP server.
>
> If the phone is connected to the internet and no SMTP client is
> installed, install a chat application which has a public API
> (e.g. https://chatwork.com) and send (encrypted) messages from
> the linux box to the phone using the API.

That could be.

>
>
>
>
> Or, if you want to go full hard-core, check out the X10 home automation
> apps, after installing some compatible hub server on a LAN box.

Mmm.

I'm inclined to test <https://ntfy.sh/>, which seems very simple.

--
Cheers,
Carlos E.R.

Carlos E. R. <robin_listas@es.invalid> wrote:
> I have that, but not disimilar from using gmail. Another client
> wastes battery (K9 did, which is why I don't have it checking for
> email except on demand).

The newer K9's seem to have fixed that issue and no longer waste
battery doing a busy-loop looking for new emails. Or at least on my
phone K9 uses a "push notification" that does not waste battery. You
may want to give K9 another look to see if it might work for your
'notification' needs.

On 2023-03-28 19:07, Rich wrote:
> Carlos E. R. <robin_listas@es.invalid> wrote:
>> I have that, but not disimilar from using gmail. Another client
>> wastes battery (K9 did, which is why I don't have it checking for
>> email except on demand).
>
> The newer K9's seem to have fixed that issue and no longer waste
> battery doing a busy-loop looking for new emails. Or at least on my
> phone K9 uses a "push notification" that does not waste battery. You
> may want to give K9 another look to see if it might work for your
> 'notification' needs.

I do use K9, only that I disabled automatic checking for new email. I
may try to enable the feature again.

--
Cheers,
Carlos E.R.

Pancho <Pancho.Jo...@proton.me> [P]:
P> Android VOIP clients were always a bit crap, precisely because
P> they lacked a reliable push notification.

Isn't the phone ringing enough of a notification?

On 3/27/23 8:53 AM, Carlos E.R. wrote:
> Hi,
>
> Do you know of an app, to be installed on an Android phone, that can
> receive some kind of notification or ping from a Linux computer, in the
> same LAN, from a script?
>
> Like for telling me some job ended, whatever. Not internet, the LAN is
> sufficient.

You could write a simple client/server setup to
do that. Just listens on a TCP or UDP port for
the correct sequence. For your app UDP might be
the cleaner way, not as many hacks probing.

Lots of sample client/server code on the net,
Python and 'C'. I've built a number of useful
things on those foundations. A non-blocking
might be best, lets you dump odd 'noise' more
easily. Python is pretty damned easy - but
you've gotta encode()/decode() in order to
deal with binary. 'C' and FPC have a 'timer'
so you can break from the listening routine
and do other stuff (outright or as a subproc)
before returning to listening.

The dead-simple client/server would do very
well - you don't need threaded servers or
forking servers or any of the other variants
meant for higher volume traffic. That means
a very small service routine. Just start with
one of the sample 'echo' servers - where what
you send gets reflected back - and it only
takes a few tweaks.

Bash and ksh have an obscure syntax for sending
and receiving to a /dev/tcp pseudo-device - and
I use it in several scripts. Probably THE easiest
way for what you're trying to do. Would not be
limited to a LAN either if you put the right
rule in the firewall.

On 3/27/23 5:08 PM, Andreas Kohlbach wrote:
> On Mon, 27 Mar 2023 14:53:18 +0200, Carlos E.R. wrote:
>>
>> Do you know of an app, to be installed on an Android phone, that can
>> receive some kind of notification or ping from a Linux computer, in
>> the same LAN, from a script?
>>
>> Like for telling me some job ended, whatever. Not internet, the LAN is
>> sufficient.
>
> No. But if your mail app on the phone sends audible notifications when a
> new mail arrives, you could have Linux send a mail to the email address
> on your phone.

That would work ok ... but it's not as FUN as writing
yer own client/server app :-)

On 3/28/23 3:00 PM, Carlos E. R. wrote:
> On 2023-03-28 19:07, Rich wrote:
>> Carlos E. R. <robin_listas@es.invalid> wrote:
>>> I have that, but not disimilar from using gmail.  Another client
>>> wastes battery (K9 did, which is why I don't have it checking for
>>> email except on demand).
>>
>> The newer K9's seem to have fixed that issue and no longer waste
>> battery doing a busy-loop looking for new emails.  Or at least on my
>> phone K9 uses a "push notification" that does not waste battery.  You
>> may want to give K9 another look to see if it might work for your
>> 'notification' needs.
>
> I do use K9, only that I disabled automatic checking for new email. I
> may try to enable the feature again.

There's good waiting/polling and BAD waiting/polling - and
the older K9 was *bad* in that respect.

If you can set polling for even every 5 minutes - and they're
not trying to do tons of things between polls - then it ought
to be better now. Hell, any Python app/service you can just
have it sleep() between checks and it uses almost zero CPU
while sleeping.

On 3/29/23 00:16, Fritz Wuehler wrote:
> Pancho <Pancho.Jo...@proton.me> [P]:
> P> Android VOIP clients were always a bit crap, precisely because
> P> they lacked a reliable push notification.
>
> Isn't the phone ringing enough of a notification?
>

The problem with android VoIP softphones is that they tend to
deregister. So the ring isn't reliable.

I never really understood this feature lack, because mobile phones do
have a reliable push notification mechanism, the ring of a standard
phone call.

Maybe Google deliberately excluded a generic push notification feature,
to stop software competing with the mobile network providers.

Pancho <Pancho.Jones@proton.me> wrote:
> On 3/29/23 00:16, Fritz Wuehler wrote:
>> Pancho <Pancho.Jo...@proton.me> [P]:
>> P> Android VOIP clients were always a bit crap, precisely because
>> P> they lacked a reliable push notification.
>>
>> Isn't the phone ringing enough of a notification?
>>
>
> The problem with android VoIP softphones is that they tend to
> deregister. So the ring isn't reliable.
>
> I never really understood this feature lack, because mobile phones do
> have a reliable push notification mechanism, the ring of a standard
> phone call.

A standard phone call is handled as part of the native "cell network"
protocol, which is why it almost always works.

VOIP is handled over the 'data channel' -- which for phones was until
recently a second class citizen in the phone/cell world.

On 29/03/2023 23:16, Rich wrote:
> Pancho <Pancho.Jones@proton.me> wrote:
>> On 3/29/23 00:16, Fritz Wuehler wrote:
>>> Pancho <Pancho.Jo...@proton.me> [P]:
>>> P> Android VOIP clients were always a bit crap, precisely because
>>> P> they lacked a reliable push notification.
>>>
>>> Isn't the phone ringing enough of a notification?
>>>
>>
>> The problem with android VoIP softphones is that they tend to
>> deregister. So the ring isn't reliable.
>>
>> I never really understood this feature lack, because mobile phones do
>> have a reliable push notification mechanism, the ring of a standard
>> phone call.
>
> A standard phone call is handled as part of the native "cell network"
> protocol, which is why it almost always works.
>
> VOIP is handled over the 'data channel' -- which for phones was until
> recently a second class citizen in the phone/cell world.
>

No, I have used VoIP exclusively for my home phone for over a decade, I
rarely use mobile/cell, The home phone data line QoS is OK, not the
problem, rings are reliable.

AIUI, speaking from my standard jack of all trades position, the
difficulty with Android is sleep states/power saving. The Android OS is
doing something to the VoIP softphone, or maybe something at or below
the network transport layer, something that doesn't happen to my
(GigaSet VoIP) home phone.

Pancho <Pancho.Jones@proton.me> wrote:
> On 29/03/2023 23:16, Rich wrote:
>> Pancho <Pancho.Jones@proton.me> wrote:
>>> On 3/29/23 00:16, Fritz Wuehler wrote:
>>>> Pancho <Pancho.Jo...@proton.me> [P]:
>>>> P> Android VOIP clients were always a bit crap, precisely because
>>>> P> they lacked a reliable push notification.
>>>>
>>>> Isn't the phone ringing enough of a notification?
>>>>
>>>
>>> The problem with android VoIP softphones is that they tend to
>>> deregister. So the ring isn't reliable.
>>>
>>> I never really understood this feature lack, because mobile phones do
>>> have a reliable push notification mechanism, the ring of a standard
>>> phone call.
>>
>> A standard phone call is handled as part of the native "cell network"
>> protocol, which is why it almost always works.
>>
>> VOIP is handled over the 'data channel' -- which for phones was until
>> recently a second class citizen in the phone/cell world.
>>
>
> No, I have used VoIP exclusively for my home phone for over a decade, I
> rarely use mobile/cell, The home phone data line QoS is OK, not the
> problem, rings are reliable.
>
> AIUI, speaking from my standard jack of all trades position, the
> difficulty with Android is sleep states/power saving. The Android OS is
> doing something to the VoIP softphone, or maybe something at or below
> the network transport layer, something that doesn't happen to my
> (GigaSet VoIP) home phone.

Yes, your statement is just a longer version of mine:

>> VOIP is handled over the 'data channel' -- which for phones was until
>> recently a second class citizen in the phone/cell world.

Ultimately that "second class citizen" problem is likely to be some Android OS
issue.

Pancho <Pancho.Jo...@Proton.Me> [P]:
P> The problem with android VoIP softphones is that they tend to
P> deregister.

The real culprit behind such problems is probably the change of the
phone's IP over time (eg. because of roaming, or switching
between IPv4 and IPv6 networks) rather than the OS or the
VoIP software itself.

When the mobile provider's and the VoIP registrar's notion of the
device's IP get out of sync with each other, chaos ensues.

The VoIP protocol is (unfortunately) too smart for its own good
with respect to IP addresses in this case... It's not really
IP agnostic, much like FTP, which can also have this type of problems.

Pancho <Pancho.Jo...@Proton.Me> [P]:
P> The problem with android VoIP softphones is that they tend to
P> deregister. So the ring isn't reliable.

You just don't get it, do you? Calling a device by its (LAN) IP has
no need for registration. Try it some time and see how it goes.

I have been using a similar technique (ie. calling a VoIP device by
IP, which actually is the remote end of a point-to-point VPN) for ages.
This type of communication doesn't need (or leak) anything from
(or to) the internet at large.

As long as the participating VoIP clients don't crash or otherwise
misbehave and the connection channel stays up, whether the registar
knows about their current availability status, IPs and audio ports
(or is able to talk to them at all) is totally irrelevant.

If you need more convincing consider the following scenario: a
VoIP device having multiple IPs (physical or virtual). It publishes one
of them (via the registrar), but (assuming it has been configured to
listen on all of them) it can also be called by anyone on the other
(non-published) networks. Do you get it now?

On 4/1/23 23:06, Fritz Wuehler wrote:
> Pancho <Pancho.Jo...@Proton.Me> [P]:
> P> The problem with android VoIP softphones is that they tend to
> P> deregister. So the ring isn't reliable.
>
> You just don't get it, do you? Calling a device by its (LAN) IP has
> no need for registration. Try it some time and see how it goes.
>

Yes, that is a good point. But difficult to test, reliably. VoIP already
works, most of the time.

Also, I don't know if my IP address does change regularly. Obviously, it
does when the phone moves between my wlan and the mobile/cell network,
but I don't know how often it changes on the mobile/cell network alone.
I don't know if that is the root of the problem. Naïvely, I would expect
a change of IP notification to handle it, but I don't know. Maybe it
would be expensive on the battery, to wake a host of apps when the
external IP changed.

> I have been using a similar technique (ie. calling a VoIP device by
> IP, which actually is the remote end of a point-to-point VPN) for ages.
> This type of communication doesn't need (or leak) anything from
> (or to) the internet at large.
>
> As long as the participating VoIP clients don't crash or otherwise
> misbehave and the connection channel stays up, whether the registar
> knows about their current availability status, IPs and audio ports
> (or is able to talk to them at all) is totally irrelevant.
>

I'm not clear, what the connection channel is? Or what stays up means.

> If you need more convincing consider the following scenario: a
> VoIP device having multiple IPs (physical or virtual). It publishes one
> of them (via the registrar), but (assuming it has been configured to
> listen on all of them) it can also be called by anyone on the other
> (non-published) networks. Do you get it now?
>

You might be right, but a thought experiment isn't going to convince me.
I would need to understand Android. Understand things like, waiting on a
socket with respect to app sleep states. There is a lot that could go
wrong, above and beyond change of IP address.

On 2023-04-02 23:34, Pancho wrote:
> On 4/1/23 23:06, Fritz Wuehler wrote:
>> Pancho <Pancho.Jo...@Proton.Me> [P]:
>> P> The problem with android VoIP softphones is that they tend to
>> P> deregister. So the ring isn't reliable.
>>
>> You just don't get it, do you? Calling a device by its (LAN) IP has
>> no need for registration. Try it some time and see how it goes.
>>
>
> Yes, that is a good point. But difficult to test, reliably. VoIP already
> works, most of the time.
>
> Also, I don't know if my IP address does change regularly. Obviously, it
> does when the phone moves between my wlan and the mobile/cell network,

You forget we are talking of LAN alone.

> but I don't know how often it changes on the mobile/cell network alone.
> I don't know if that is the root of the problem. Naïvely, I would expect
> a change of IP notification to handle it, but I don't know. Maybe it
> would be expensive on the battery, to wake a host of apps when the
> external IP changed.

The IP does not change in the LAN.

>
>
>> I have been using a similar technique (ie. calling a VoIP device by
>> IP, which actually is the remote end of a point-to-point VPN) for ages.
>> This type of communication doesn't need (or leak) anything from
>> (or to) the internet at large.
>>
>> As long as the participating VoIP clients don't crash or otherwise
>> misbehave and the connection channel stays up, whether the registar
>> knows about their current availability status, IPs and audio ports
>> (or is able to talk to them at all) is totally irrelevant.
>>
>
> I'm not clear, what the connection channel is? Or what stays up means.
>
>> If you need more convincing consider the following scenario: a
>> VoIP device having multiple IPs (physical or virtual). It publishes one
>> of them (via the registrar), but (assuming it has been configured to
>> listen on all of them) it can also be called by anyone on the other
>> (non-published) networks. Do you get it now?
>>
>
> You might be right, but a thought experiment isn't going to convince me.
> I would need to understand Android. Understand things like, waiting on a
> socket with respect to app sleep states. There is a lot that could go
> wrong, above and beyond change of IP address.

It is not a thought experiment, it is how things work.

VoIP can be done inside a network by knowing the IP of the destination
without a registrar. Try it.

--
Cheers, Carlos.

On 03/04/2023 02:40, Carlos E.R. wrote:
> On 2023-04-02 23:34, Pancho wrote:
>> On 4/1/23 23:06, Fritz Wuehler wrote:
>>> Pancho <Pancho.Jo...@Proton.Me> [P]:
>>> P> The problem with android VoIP softphones is that they tend to
>>> P> deregister. So the ring isn't reliable.
>>>
>>> You just don't get it, do you? Calling a device by its (LAN) IP has
>>> no need for registration. Try it some time and see how it goes.
>>>
>>
>> Yes, that is a good point. But difficult to test, reliably. VoIP
>> already works, most of the time.
>>
>> Also, I don't know if my IP address does change regularly. Obviously,
>> it does when the phone moves between my wlan and the mobile/cell network,
>
> You forget we are talking of LAN alone.

No, I understand that, but I have 10 years experience of Android VoIP
softphones being unreliable. I'm not sure why they are unreliable, just
a history of mild interest, and consequent prejudice.

Someone can say my issues are due to changing external IP, that it won't
happen in a LAN environment, and they may be right, but I don't have
evidence of that.

Suggesting one potential failure mechanism does not exclude other
mechanisms. You haven't excluded the possibility that aggressive power
saving requirements, and consequent sleep states, cause the problem.

If someone could point to real life experience of an Andorid VoIP
clients working reliably on a LAN, with direct IP calls, or probably
more tractably via a LAN base PBX such as Asterisk, I would be more
convinced.