Extending networking/socket programming functionality of a qml project

qcoderpro

Chatting the way that example provides with many chatters and a chat room is not what was needed. Furthermore it says: Launch several instances of this program on your local network and start chatting! What's needed is beyond local network.

The projects work fine in all the following ways, when:

1- they're both running using Desktop kit (on Windows)
2- they're both running on the same virtual Android device (on Windows)
3- the server is run using Desktop kit and client is running on a virtual Android device.

But the intention is, for instance, you install one of the apps on your Android device and send the other to your friend in another city and you two can exchange messages together, each time a message from you or they. I hope it is now obvious for you all.

If code for the projects is required I can share it here or anywhere else you find suitable.

SGaist

You have an architectural issue here. You will try to connect to a server which might change IP address at any time. You also need a secondary communication channel to share said address as well as port number. Secondary channel that you will have to use pretty regularly in order to be able to keep the communication going.

Also, what about messages that cannot reach the other phone because its offline, out of network access, etc ?

KDAB wrote a pretty interesting article about building a chat application which I recommend you to read.

VRonin

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

you install one of the apps on your Android device and send the other to your friend in another city and you two can exchange messages together

Unless you relax the security settings of one of the devices this will not work. You'll need a central server. This is not a restriction of the Qt framework, it's how all chatting applications work (the most famous messaging apps show the famous "double tick", one tick when the central server receives it, one tick when the second person receives the message).

You can also take a look at https://wiki.qt.io/WIP-How_to_create_a_simple_chat_application where the chat logic is separate from the UI so it's easier to just replace the UI in QML. In any case you will need a server application that lives in a machine that is set up to accept incoming connection from the internet (client machines usually can't for security reason) and 2 clients that connect to it

qcoderpro

@SGaist

You have an architectural issue here. You will try to connect to a server which might change IP address at any time.

Does it mean that from the time the server provides us with the IP (and port) on, that IP ( and port) may change and not usable by the client? Is it because the IP is public and non-static, so it can change at any given second?

You also need a secondary communication channel to share said address as well as port number. Secondary channel that you will have to use pretty regularly in order to be able to keep the communication going.

Does it mean that such a channel will keep the IP (and port) static to be usable on the client side? If so, what is that channel,please?

Also, what about messages that cannot reach the other phone because its offline, out of network access, etc ?

For simplicity reasons, we try to keep both users online throughout our connection for testing it.

qcoderpro

@VRonin

Unless you relax the security settings of one of the devices this will not work. You'll need a central server. This is not a restriction of the Qt framework, it's how all chatting applications work (the most famous messaging apps show the famous "double tick", one tick when the central server receives it, one tick when the second person receives the message).

Does it also mean that for such a simple communication (exchanging string messages) through global Internet we need a static IP/central sever? (like what SGaist believes I guess.)

Also, thank you both for your links to those two examples, but consider my current situation, please.
My two QML projects (with 3 files for each: .h, .cpp, and .qml - totally 6 files) contain nearly half the number of code lines of the two QWidget Fortune client/server projects, while the qml projects are different in two aspects:
1- the sender is able to send any string message to the receiver
2- the receiver is also able to send messages back.
It was a huge jump in my socket programming/networking learning journey, a great part of which was possible because of your help.
I took a look at the two links you sent me and they are undoubtedly very worthwhile I'm sure, but they're also very vast and huge for my current level! :(
I decided to step forward and learn new things step-by-step. After gaining a goal in my projects, I like to extend them only one step more each time. That way I guess I can make progress better and easier without being bewildered and confused with lots of new and complicated code.
I hope you understand me. :)

SGaist

Here is the thing: network programming is not simple as soon as you put internet in the mix.

Hence, taking the time to study more complexe but detailed examples will help you faster than trying to make things work in a complexe setup. The chat is a good example: simple implementation for local networks, it requires more bricks when you start making a service that shall work across networks on different devices.

qcoderpro

@SGaist

Here is the thing: network programming is not simple as soon as you put internet in the mix.
Hence, taking the time to study more complexe but detailed examples will help you faster than trying to make things work in a complexe setup. The chat is a good example: simple implementation for local networks, it requires more bricks when you start making a service that shall work across networks on different devices.

Yeah, sure. I understand and will certainly study that chat example in near future, but for now I just like to extend my two projects so that they can work through global Internet.

Will you answer the questions I asked above, please? They're important for me.

SGaist

Static address is not required if you have a DNS resolvable name.

VRonin

Your problem is not an application one (if it works over LAN it means that you programmed it correctly), it’s an infrastructure one.
If you don’t have one of the two devices set up to accept incoming connections and with a way to know what IP address to connect to (via either static ip or registering with a DNS) then you can’t do it.
Neither of these conditions, however, depend on the application code, it’s just device setup

qcoderpro

@SGaist

Static address is not required if you have a DNS resolvable name.

Although I've forgotten most of the things from university lessons (years ago) but yet can recall that a DNS works much like a phone book by managing the mapping between names and numbers. Do you mean that I need to setup a DNS resolvable name? Will you recommend a tutorial on this please?

SGaist

Nobody suggested that you install a DNS server. You need to get an address from example from noip or another service.

qcoderpro

@SGaist
Aha, you mean to get an IP address from noip.com for instance, or another website like that.
But how that IP address will work on my projects, please?

jsulm

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

But how that IP address will work on my projects, please?

Your device will get the IP at runtime using DNS.
If you access www..google..com you also do not enter an IP, right? But in the background your machine gets the IP for www..google..com via DNS.

qcoderpro

@jsulm
I mean, is the story this way?
When both projects are run, the server will get the IP address (provided by noip.com). The client also has that address (in its code) so it connects to it. Then they can exchanges messages.
Right?

If so, how about the port number!? Don't we need it?

jsulm

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

The client also has that address (in its code) so it connects to it

Do you mean IP address? No, client also has to get the IP first.

"If so, how about the port number!?" - port number can be fixed (like 8080 for HTTP).

qcoderpro

@jsulm
OK so both projects need to get the IP address at runtime and since the port is set to 8080 (as you said), they can connect and start exchanging messages. Right?

jsulm

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

as you said

I did not. It was just an example.
"they can connect and start exchanging messages" - if they can get the IP then yes.

qcoderpro

@jsulm

OK I visited the page for noip.com and read a number of services they offer, some of them are free, but limited, as expected.
Are the steps to get the IP needed for the projects to work, as below, please?

1: Create an Account.
2: Confirm Your Account.
3: Log In to Your Account.
4: Add a Host or Domain to Your Account.
5: Making Your Host Dynamic.
6: Configure Your Router.
7: Run Your Services

I signed up and then went for adding a hostname but for the domain there're many options, as follows:

Is what I've done so far right, please?
What to choose for the domain, please?

SGaist

yes
that's up to you.

qcoderpro

@SGaist

yes

So I need to go through all those 7 steps. Right?

that's up to you.

I've no idea what to choose and for what, ect. since I'm new in networking and my purpose for using noip service ( (for now)) is just to use it for my two QML projects mentioned above. Which domain do you suggest, please?