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Android DownloadManager with gRPC

Currently working on an API which make the client (Android/Kotlin) being able to download a video from the server. With a traditional HTTP URI it would be a pretty easy task, I would just DownloadManager and the problem is solved. However, I'm using gRPC (c++) for the server.
I currently have a solution with Kotlin flows which basically take the unidirectional stream from the server and consume the file chunk to store them in local file. However, even if it works for the major parts, It has a lot of corner cases and that is why I want to use DownloadManager. For further information on what I have currently please check: Handling file download with gRPC on Android
After looking for a solution for a little while now, I found that it is possible to map the RPC call to REST API by using this project and basically do something like:
rpc Download(DownloadRequest) returns (DownloadResponse) {
option (google.api.http) = {
post: "/v1/download"
body: "*"
};
}
or use a YAML file to configure the google API.
All of this seems to be pretty convenient while using Google Cloud and Golang but I'm creating a standalone server in C++.
So there are two questions here:
Is it possible to serve static file in a REST way with gRPC c++
Is there another way to use DownloadManager with gRPC ?

As the commenter on the question suggested, gRPC is for structured data not raw file downloads. Trying to map between a URI and the RPC call would not be enough to make DownloadManager work with gRPC, because the gRPC server is going to send and expect additional data beyond the raw file itself that will not be understood or sent by DownloadManager.
You can certainly use gRPC server and client to send large files, but it's not going to have the same set of features built-in for large file downloading (such as resuming your download later if the connection is broken) as using something like a HTTP server + a specific file download library/client. I would recommend just running a separate HTTP server for your file download needs.
[crossposting my answer from the grpcio mailing list]

How does android retrieve data from a website?

I'm new to android, I'm trying to build an android app that is a front for a web portal. For example, Airbnb. They have a website, but they also have an android app that, using it's own layout, will show listings from their website.
There are many websites that teach how to or even directly convert your website to android apps. However, this will result in an app that loads too slowly and is unresponsive due to CPU usage.
Could anyone share any tutorial/guide to learn how to do this myself?
Million thanks.

To actually load data from a web server you're gonna need and API which usually delivers the proper date using JSON or XML format so that you can properly parse and display that data. Building this API is in it self a complete course on its own.
But connecting to and requesting data from the API is usually done using some networking libraries. These are some of the better know libraries for this purpose.
OkHttp: A complete library with a set of tools for handling network connections and HTTP requests.
RetroFit:Type-safe HTTP client for Android and Java by Square, Inc. which is built on top of OkHttp.
Async-Http-Client:
The Async Http Client library's purpose is to allow Java applications
to easily execute HTTP requests and asynchronously process the HTTP
responses. The library also supports the WebSocket Protocol. The Async
HTTP Client library is simple to use.
There tons of other good libraries.

its called webservices
Through android you get data in form of json from a web server and then return in custom view as you want.
Follow this link hope it will help
Step by Step Method to Access Webservice from Android

you would have to write an API/Web service or use if already exits to fetch data from web server. Basically the concept is that, the website itself must be pulling data from some database, so write an API which would fetch the data from same API and return JSON data and consume the API from your android app.
If you know PHP refere to this for the help :http://www.codeproject.com/Articles/267023/Send-and-receive-json-between-android-and-php

You can write WebService, in programming it generally refers to a web page(ex. Airbnb), that can be called from your android application which can pass in data to it, or receive data from it.
WebService is basically like a 'method' or 'function' in a normal programming language; except you're calling it over the internet.

The first thing is you have to create a Web Service. The Web Service will be your "bridge" to consume the data from other Website like airbnb or others and return the data to your android through json format for example.
You can create a Web Service using many languages like C#, Java, PHP, etc. I would like to recommend you to use the language that you know the most.
You can try to google this
Cheers

Socket.io and node.js example in android

I am new to socket programming i have to use socket.io and node.js to connect with my server host in android so can anyone please just describe me the programming example of how to connect to server in android. And if possible please give some help regarding node.js and socket.io. As i have searched everywhere on google but not able to find out the proper example.
Thanks

You can just have your web service be REST base.
Your Android application can just talk to your web server via REST and receive data json or xml whatever you fancy.
So with node.js you should set up routes.
An example would of a route would be
www.example.com/users via GET post would return a list of users either in JSON/XML
For your android application you need a library, I believe there's a built in one already, to make request for certain routes such as www.example.com/users via GET method and write the logic to expect JSON or XML and parse that.
I just googled this:
Android: https://github.com/koush/ion
As for node.js you just have to build route...
I think is would be better:
websocket api to replace rest api?
It actually invalidate my answers sorry, REST and websocket api are different.
I have no clue what problem exactly you have. But you should break your problems down to small part. And google and search for answer for each smaller part which would make your life easier to google.
Get your webservice up first so that your android software can consume stuff, build a prototype and then build a prototype of android app that consume data from that webservice.

Creating Web Service for Android Application

I've been reading some info about Web Services for Android using SOAP or REST but I've never created a web service so I have many questions about this.
I'm developing an Android App where the users answer some questions and for each user an XML file is generated and saved in the device.
Here are my queries:
What I would like to do is to send these XML files from the devices to the Web Service and also sometimes to retrieve all the files to any
device.
Do I need to convert these files into Byte or just send the XML?
Are these actions possible with the Web Service or will you use Java Sockets? In case you prefer the Web Service, what would you use:
REST, SOAP.
I would appreciate some links to tutorials and piece of advise.

Use SQL Server to manage the data on your desktop and create a web-service in .NET on Visual Studio.
Then connect to the web-service in your application and set/get data from the DB, using web-services. You can use either XML or JSON to transfer your data between the phone and the server.
There is no need for the use of Java Socket API for this.
Links which might be useful :
How to make a web-service in .NET (does not include the implementation in Android) : http://srikanthtechnologies.com/blog/dotnet/wsdaljava.aspx
How to connect your service with Android :
http://seesharpgears.blogspot.in/2010/11/basic-ksoap-android-tutorial.html
http://www.codeproject.com/Articles/304302/Calling-Asp-Net-Webservice-ASMX-From-an-Android-Ap
http://adrianandroid.blogspot.in/2012/05/access-c-net-web-service-in.html
Note: I have never worked on RESTful services. My work has always been on SOAP and hence it remains my preference.

Your final choice of how, exactly, to architect your app, is going to be based on all sorts of things that you haven't included in your questions: your experience, the experience of the other developers in the project, so on and so on.
I will say this, however. REST is deep in the heart of Android. If you decide to go with REST and, possibly, JSON instead of XML (there is, almost certainly, no reason to use byte arrays), you will find that Android's architecture supports you. SOAP and such and you are on your own.

Needs workflow ideas for Android app

I'm planning on writing an android app that can view and update data on a local network Oracle DB.
I have already written a python script which checks the oracle db every couple of minutes and writes out XML files which I then plan to parse through my android app to display the data.
As I mentioned though this will only work if the android device is part of the same network (either connected locally or through a vpn), and the XML will be stored on a Unix server.
The question is how to access that Unix server with the android app? Can I use FTP via an android app, or should I be looking to change the python script to send the XML to an easily retrievable location?
EDIT To clarify what you mean, you have a web service running on something like tomcat, the client sends a request to get the data from the oracle db (can also use some form of authentication), the web service responds and sends the data in a format (XML, JSON etc.), the client then sends a request back to the web service to change some data on the oracle db, and in turn it does the clients bidding?

Normally you would create a web service to provide data to mobile clients. There are several reasons for this:
Web services are accessed via HTTP/HTTPS which is a standard protocol and is guaranteed to work on all networks. Corporate wifi networks are especially notorious for locking down protocols except for web and email.
Web services compared to static XML files have an advantage of creating response on the fly. Which means that data will be current.
Web services can take some input parameters and create response based on this parameters.
Authentication: it is a common approach to implement username/passord authentication in the web service, especially if you serve some private data.
Update:
REST is a very popular type of web service. Look at some implementations in Python: Recommendations of Python REST (web services) framework?

This book helped me a lot: http://oreilly.com/catalog/9780596529260
REST is a way of designing your web service. Folks much more intelligent than you and me have divined that all of the work needed for something to work on the net can be handled through a combination of HTTP status codes, HTTP verbs like POST, GET, DELETE, PUT etc. and a clear hierarchy of resources (nouns). It sounds very limiting but it's quite beautiful when it all works together.
Have a look at the Facebook Open Graph API (developers.facebook.com) to get an idea of what a proper REST service looks like.