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C# server-client implementation with TCP

I want to create a simple messaging app that uses tcp protocol to communicate, including with multiple people. Messages get sent to the server, which distributes them to all other clients. At the moment, I have it fully functioning and it works perfectly - on a local computer and a local network, using the ipv4 address.
After an extensive Google search, I discovered that to communicate from a different network I need to port-forward my server. However, how do I make my server able to communicate with clients without all the clients port-forwarding? As far as I'm aware, not everybody's device is port-forwarded.
So, how do I implement this? Is it possible with just C#? Or did I misunderstand something, and port-forwarding isn't really required?
Thanks for all the help.

Why don't you use SignalR. I think it will be best for your problem.

use socket to send data on internet

When I send data using socket in C# on LAN, everything works fine, but how do I send my data over the internet. How to send while the sever I create uses the ip from my compute (private ip)
Can someone suggest on how can I achieve this, basically I should be able to send data anywhere over the internet, not just on LAN.

These days most computers have a router with a firewall between them. Routers, via secreuity design, stop direct access to the computers behind them and their local network.
Yes you will either have to
configure the router to map through a specific port to one of your computers.
Or, the more common way to do this is using a central hub, ie a Web service as an intermediary. This way no firewall are needed as both computers are only connecting one way (out). You could use a wcf service or Web api or many technologies to achieve this and usually you'd use a database to store you game state which makes it persistent

Two-way Communication between Server and Clients

Situation: We have a web application running on a server. This application needs to fetch data from some other PC(Clients), which are on a different network.
On the clients' pc there are WCF hosted in Windows Services using its their local Sql db. i want to make duplex communication between server and clients for share data with each other.
data share mean share data-table,data-set,string etc between clients and server .
Problem :
1) I have no control over the firewall, proxy, NAT on the client side PC. Mostly company Employee PCs have lots of network security e.g firewall block ICMP traffic and some port too, some Router might be Disabled port-forwarding etc etc , client can change network place.
I don't want to make any setting on client side Router,proxy,firewall though .
during communication how can i handle that's kind of issue of client side?
as you know skype is working perfect in that situation.
firewalls very often block inbound connections to clients; the client may not be reachable from the server, it may be using NAT translation behind a router and so cannot be contacted without port forwarding being set up on the router and some new router disabled port forwarding .
2) On clients side there is no IIS .
I don't want to allow remote access on clients PC.
There are more than 100 Clients and only one Server. one server need communicate with many clients on different network .
3) One side my client application is using window application and wcf hosted in window service ,Other side on my server i'm using Web application . so its mean communication is between desktop pc and web pc , that's issue .
If both using a web application then it was not issue to make duplex communication.because i know WEBRTC is fit there lol.
Technology which i had already test and find issue
WSDualHttpBinding: Not work if client behind NAT. check this for detail click here
MSMQ : its bad technique if clients more than 1 and performance issue also because its use RAM memory . check here click here
Xsocket: Its also not work if ICMP traffic block by firewall on client. check here click
WebRTC: Its work fine but its support web to web communication .as my client side i have win app.
Socket.io: Its need to set up node.js and many other thing , hard to implement because i need implement on existence application , i am not making new application.
C# Socket Program: Its wouldn't work if client behind NAT.check here click for detail
Service Bus relay: Its not free even for testing .
socketPro: I studied i find its good but i can't find any right sample on google .so that i could test that.
Genuine Channels: I can't find any sample on google .
Lets see SignalR issue .: Server side i run a console application and Client side i run two application ,one is console and other web. when i was running console client application than it was not initiating connection with Server but when i was using web client application then it was working fine.
sample link is here SignalR two way communication
I can't understand why thas??
Please tell me What is best most secure and fast way to handle this situation? what approach should i use ?

SignalR seems to fit for this solution, because it's flexible.
It negotiates the fastest available channel of communication and that is what you are looking for.
You should investigate the problem with it and signalR will eventually work.

I'm using SignalR extensively to communicate between the servers (C#), between server and mobile apps (C#, Xamarin, iOS, Android). The servers are at different locations and the mobile apps can be anywhere. It all works very reliable.
Take a look at: http://www.asp.net/signalr/overview/deployment/tutorial-signalr-self-host and here http://www.asp.net/signalr/overview/guide-to-the-api/hubs-api-guide-net-client

I've been working in my spare time with sockets (admittedly in c++, not c# but there shouldn't be a difference), and I've never had an issue connecting to clients behind a firewall/router, even without port forwarding.
Routers and firewalls generally don't like server-like programs, eg. programs that bind the socket to a port number. Does your client do anything related to binding? Because it shouldn't.
Needless to say, I would suggest a socket program. The way I see it, it's the most flexible way.

Sockets: client finding server automatically via name, not IP

I got a client program in Java (Android app), and a server program in C#.
They communicate via Sockets over an internal network.
Problem:
The client needs to have the server's IP address stored, to be able to connect. So, the server needs a static IP.
But now I got to a point I can't have a static IP anymore, so the client has to find the server when it starts up, somehow.
I thought you could use the computer-name to connect via Sockets, but that didn't work for me.
Then I had an idea to just do a broadcast with a basic request, and see who answers (the server from the correct IP), but I have no idea how I can do a broadcast and wait for multiple responses.
And then I also have to find the broadcast address.
Are there any techniques out there that I don't know and haven't come across yet?
Any help is much appreciated! :)

What you are looking is a hostname discovery service. JNDI is an API for discovering hostnames, but it is for java applications.
check this documentation how to use JNDI from .NET framework

Easiest for two way communication over the internet using C#

What do I use for two way communication over the internet without the necessity to open ports on the client side?
Users won't agree to open ports and do port forwarding on the client side although everything is possible on the server side.
But,I need to accomplish two way communication..
How do I go about achieving this?
It doesn't matter whether its WCF or remoting or webservices...
I just need a quick and fast way to just get the concept to work out and distribute the application.
ofcourse,it's going to be through the internet.
Please help..
Thanks
Edit : Please note that i need to connect multiple clients and maintain a session for each client.

WCF supports duplex HTTP bindings.
As long as the initiating client can access the service, a callback contract can be defined to call the client. It simply keeps the HTTP connection once the client has initiated it.

It depends what you want to do. Duplex WCF can work, but through NAT and Proxies it becomes somewhat "iffy" because it depends on the client opening a WCF endpoint and maintaining the connection.
I wrote a beginners guide to WCF callbacks a while ago - it's simple enough to do, but you'll need to test it a lot, from various client setups.

Connect via TCP (raw sockets, or higher implementation) to a your central server.
Your server should have an application that listens to a specific, well known, TCP port.
Each client connects to your server, using the specific port, and "logs in".
Write an application protocol above the TCP (authentication, session management, etc.), and there you have it, since a TCP connection, once established, works for both directions.