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.NET desktop client app: sockets or HTTP requests? [closed]

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I'm trying to set up a Windows service that can communicate asynchronously with a server, the idea is to transfer some strings. The format, well, it really doesn't matter that much.
So, in the local network, I'm cool, I even wrote a simple mobile app to test it with requests and it just works.
The problem is I now have to make it work from outside the network, and to make it happen I would have to forward the port from the router configuration, and that is really not an ideal scenario for deployment on user machines.
I've read that is the thing you normally use sockets for, but as far as I understand, at least with .NET, the server has to have the same framework (please correct me if that is not true), and in my case the server is not .NET.
Honestly, I don't know much about client-server interaction, and I have a huge conceptual blackout when reading the official Microsoft documentation, so scratch that. I've caught glimpses of WinSock and RPC from the docs, but a C# implementation feels like duct tape, and really a last resort.
That said, I reckon I need to make six questions:
Plain HTTP is a bad idea. Right?
Given the scenario, is sockets what I need? And if it is,
How can I implement that on the server? Also,
Is it better than using RPC?
How exactly does RPC work anyway? What do I need to read before the official docs?
What does a socket do to actually let the client receive an asynchronous call from outside the local network? (need it, I read it's possible)
Please forgive me if I am mixing concepts here, and thanks for reading.
NOTE to moderators: If this is a duplicate question in any way, or off topic, or invalid for any other reason, please help me first by pointing me in the right direction. I tried to give it a good search before posting, but since I am not so familiar with most concepts, I might have missed the one. Thanks!

Some answers here:
The problem is I now have to make it work from outside the network, and to make it happen I would have to forward the port from the router configuration, and that is really not an ideal scenario for deployment on user machines.
Portforwarding is only needed when connecting from outside the netwerk to a computer inside network (behind a router). So if a user machine connects to a computer directly on the internet, you don't need portforwarding. If a computer from the internet connects to a computer in your local network, you need to forward a port in your router. So it only affects your network.
I've read that is the thing you normally use sockets for, but as far as I understand, at least with .NET, the server has to have the same framework (please correct me if that is not true), and in my case the server is not .NET.
No, A socket from .NET can communicate with any implementation of socket from another language/platform. Only when communicating binary, you should be aware for endians.
Honestly, I don't know much about client-server interaction, and I have a huge conceptual blackout when reading the official Microsoft documentation, so scratch that. I've caught glimpses of WinSock and RPC from the docs, but a C# implementation feels like duct tape, and really a last resort.
In my opinion .NET has a solid base for handling sockets. There are many technics implemented. The async sockets are very scalable for many clients
That said, I reckon I need to make six questions:
_Plain HTTP is a bad idea. Right?__
Why would you consider Plain HTTP is bad? This is very usefull when the server is writting in other languages, like PHP/Python/ASP.NET anything that uses HTTP. If you're sending user private information, you should hash/encrypt it
Given the scenario, is sockets what I need? And if it is,
Depends on how to connect to the server..
How can I implement that on the server? Also,
Is it better than using RPC?
I only used RPC in form of WebServices, You can only use this, when de server has implemented it. There are some benefits to WebServices.
How exactly does RPC work anyway? What do I need to read before the official docs?
Read more here: https://msdn.microsoft.com/en-us/library/ms950421.aspx
What does a socket do to actually let the client receive an asynchronous call from outside the local network? (need it, I read it's possible)
There is no difference between communicating between inside and outside the network. Directly communicating via sockets is always asynchronous.
Regards,

You should use Websockets. I don't know why you saying that the server and client should have the same framework, this is not the case, I have used it with C# client with NodeJs backend.
https://msdn.microsoft.com/en-us/library/system.net.websockets.websocket(v=vs.110).aspx

Email vs FTP Server for Transferring many Small Text Files [closed]

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What are the upsides to using an FTP server (hosted by a third party) to transfer (and maybe store) files when compared to just sending through email? The language of choice is C#.
Email looks easier to implement and if it was going to Gmail then server hosting and upkeep would not be a worry. However, I am not experienced with FTP servers and don't know how big of deal setup and upkeep is on them. All that is being sent is a bunch of text files, most likely each under 1 MB. Security is not a big deal at this point, but I am curious which is more secure without doing a lot of extra setup work.

Emailing means you have no guarantee that the file is received at the other end, or in a timely manner. Maybe this is not important for you? Emailing certainly would be easier to program up compared to FTP.
On the other hand if you use one of the many FTP libraries available for .NET then have complete control. You could include the library in a C# windows service to do the transferring seamlessly for you including exception (error) processing and notification.
Personally I'd take the opportunity to learn about FTP (its easy). You would of course require a FTP service to be setup on your server. All part of the learning.

I don't know your specific use case, but it sound like FTP is more appropriate than email for transferring and storing files. I mean it is called the "File Transfer Protocol" for a reason ;) The upside of FTP over Email is that it is designed for files while email is designed for email messages - it will be more difficult in automating the management of file attachments in email.
Setting up an FTP server is not difficult. Check out FileZilla:
https://filezilla-project.org/download.php?type=server
Sending files via FTP with C# is not difficult either. Here is question on that:
Upload file on ftp
BTW, again without knowing your requirements, there are also cloud services like Dropbox and Box.com that have APIs that might be even more appropriate for you.

MQTT vs. XMPP Which Should I Choose? [closed]

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Overview
I am sending messages back and forth between a client (Android phone) and a Server (Windows Server). Using a persistent connection over TCP, which protocol would be the best solution. I am looking at performance, scalability, size of messages, and battery life. The messages must arrive at the destination in order and can not be duplicates.
MQTT
This seems like the better solution, but there seems to be little examples of large implementation with lots of users. I am not sure if I can integrate this into the windows server, or if it would have to be another application or server running. Finally there seems to be a lack of information on it in general.
XMPP
This seems to have lots of implementation, examples, and even a book : ). However the main purpose seems to be for instant messaging clients and things like Google talk. Will this be an optimal solution to messaging between server and client. I know currently XMPP is mostly used in client to server to client architectures.
Please correct me if I am wrong and thanks in advance for any guidance.

It depends on what you are trying to do and what hardware you are running.
MQTT has very low keep-alive traffic. XMPP is a an IM protocol, and has a much, much higher overhead in handling presence messages between all the clients.
If you have a small memory footprint constraint, then having to handle the XML parser may make the use of XMPP impossible.
Keep in mind that MQTT stands for Message Queue Telemetry Transport, i.e., it is a transport protocol and does not define the message format at all - you will have to supply this; XMPP is an Instant Messaging protocol which carefully defines all the message formats and requires that all messages be in XML.
In addition to all this: MQTT is a publish subscribe protocol, XMPP is an instant messaging protocol that can be extended (using XEP-0060) to support publish subscribe. You need to consider this when you architect your system.
We are finding MQTT to be the quiet achiever. Your milage might be different.
It all depends ...
Track down the recent announcement by LinkedIn where they discuss their use of MQTT in their mobile app.
Cheers
Mark
(BTW Andy was slightly off in his reference to us. We are at Centre for Educational Innovation & Technology (CEIT), The University of Queensland, Brisbane, Australia)

I think that in short the MQTT advantages over XMPP are:
Throughput capacity: less overhead, more lightweight
Binary vs plain text
QoS in place (Fire-and-forget, At-least-once and Exactly-once)
Pub/Sub in place (XMPP requires extension XEP- 0060)
No need for an XML parser

I think you are probably correcting your assessment of XMPP in that it is a primarily chat-oriented protocol - it is also quite heavyweight and uses XML extensively making it verbose. I know that folks at CEIT at the Uni of Brisbane have specifically studied the differences and optimal uses for the two protocols. MQTT is very lightweight and low power - it has been used for telemetry and sensor applications for over 10 years and has been deployed on a very large scale by IBM and partners. Folks are now finding that a simple protocol like this is ideal for mobile development.
What exactly are you looking to achieve? The mqtt.org site aims to provide good links to content. There are also IRC channels and mailing lists about it. How can we help?

C# P2P Instant Messenger General Basis Help [closed]

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I want to start a simple windows P2P instant messenger in C#, similar to AOL, ICQ, etc, but much more simple (plain text messages between 2 guys)
I don't need examples on how to do it. I can find them myself.
What I do need is a general idea of how instant messaging works (P2P, not multichat) without many technical details.
For example:
Will I need a main server to make the communication between user1 and user2 happen or user1 can send the strings directly to user2? How is this called?
If user1 is logged in, how does he know of an incoming message from another user (or the online status of their friends)? Does the chat client app check every X seconds with a main server?
Any clues that might help me clear the general data flow idea will be very much appreciated.
A flowchart may also be helpful if you find one to share.
Thanks in advance.
UPDATE (NEW QUESTION) - July 6
Let's say the user had successfully logged in, and the app needs now to get and populate the list of contacts (saved on my apache/php/mysql server).
How would you implement the data retrieval (important) and later population of the contacts list? Is WebClient.DownloadString[Async] a good approach? Is there a better way?
How often should the app check for updated list (online/offline statuses). Recommendations accepted.
How can I parse JSON data on C#.NET (Visual C# Studio 2010)
I will get JSON strings.
Thanks!

If you really want to build a p2p app, there should be no server. However, this is not straightforward.
There are lots of different approaches to creating a chat system, mostly involving servers. Research comet (a good solution if implemented properly, terrible otherwise), polling (checking every x seconds) or using sockets, however there are lots of issues to be considered - and caveats, particularly firewalls/nat routers. A socket solution could potentially be 'p2p', but the polling and comet ones are not.
For your use case, I would go with a simple socket solution (one side as server, one as client) and configure your router firewall by opening a port at the server end.
You could extend this so that both sides could be both servers (listening on a port) and clients, so you could both 'call' each other.
You will need to have a permanent ip, or use a service like dyndns to get this to work properly.
Update
Yes, DownloadString or DownloadStringAsync would be a fine method.
How often is really up to you. I assume that this is only for a few users from what you said in the question, so you don't need to worry about overloading the server. Once a minute sounds reasonable, but once a second would proabably be fine too if you feel that way inclined... Parsing JSON in .NET answers your final query.

How do I read incoming mail using C# [closed]

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I am looking for a solution to allow me to read incoming emails. The three methods I can think of to do this at the moment are:
Create an Email Server parsing emails
Hook into an existing exchange server
Hook into outlook that is already set up with an email account
What is the best way to do this? And how does one go about implementing it?
Thanks

If you are already dealing with an Exchange server as the mailbox host I would suggest leveraging that via IMAP (preferred) or POP access. Recently I developed a solution that accesses a specified mailbox via AfterLogic's MailBee.NET IMAP component which I think is worth the recommendation. They have a standard trial version and reasonable pricing. Also if you go this route either POP or IMAP automation is flexible enough to work with almost any mailbox server platform; It doesn't have to be limited to Exchange environments.
There are also free .NET IMAP components out there that may do the job as well. In my limited research I found that the free alternatives didn't quite meet all of my requirements or were not as easy to learn but your situation may differ. For completeness, here is a list of alternative / free IMAP libraries I considered before deciding to spend the money on MailBee:
ImapX - http://hellowebapps.com/products/imapx/
LumiSoft.Net Imap Client - http://www.lumisoft.ee/lswww/download/downloads/Net/
InterIMAP - http://interimap.codeplex.com/
To address the 2nd part of your question... The implementation in my recent project involved writing a very simple console application that references the MailBee.NET IMAP library. The console application has a standard config file and accepts command line arguments as parameters. We define Windows scheduled tasks to run the console application according to our process needs. I am sure you could do this any number of other ways but this was the simplest approach for our needs.

I know this is an older thread but I wanted to add a link to a great open source Imap library called ImapX2: http://imapx.codeplex.com/
I tried most of the links in this thread to varying degrees of success but I found that the ImapX2 library work the best according to my needs.

Use existing IMAP server and IMAP component for that.
Creating your own IMAP server is a big security risk in my opinion.
There are free components, but most of them have problems with national characters and 'not standard' email messages...and there is none support (LumiSoft.Net is abandoned for almost 2 years)
using(Imap imap = new Imap())
{
imap.Connect("imap.server.com");
imap.Login("user", "password");
imap.SelectInbox();
List<long> uidList = imap.Search(Flag.Unseen);
foreach (long uid in uidList)
{
IMail email = new MailBuilder()
.CreateFromEml(imap.GetMessageByUID(uid));
Console.WriteLine(email.Subject);
Console.WriteLine(email.Attachments.Count);
}
imap.Close();
}
Mail.dll also includes SMTP component and template engine so you can send replies easily.
Disclaimer: I'm involved in the development of this commercial product.