I have a client-server based project implemented with boost::asio. It works fine if client and server are running in the same network, let say server ip=192.168.2.20 and client ip=192.168.2.100. But if I change the ip address of the server to 192.168.3.20 the connection is not astablished, I get socket timeout. At the same time I'm able to ping 192.168.2.20 from the server's host( I mean from 192.168.3.x network ) and I'm able to do it vica versa.
What could be a problem here?
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I created a multi-threaded client/server application that can send messages to each other at real time. Everything works perfectly, but I want to be able to send messages over the Internet. From what I understand, I need to do port forwarding to be able to make my server reachable for the clients. I then set up my port forwarding options by providing a port (9991) and then my Macbook Air's IP Address (192.168.0.1).
I then tried to connect to my server using my public server IP (let's say 197.132.20.222) and it didn't work. I then tried to see if the port forwarding worked by using this website: https://www.yougetsignal.com/tools/open-ports/ and I realized that the connection was closed. I also tried the command nc -vz 197.132.20.222 9991 while running my application and the connection is refused.
I'm using a JavaFX application, and for my server side I use a ServerSocket with port 9991. For the client side, I use a Socket and set the IP Address to my public router IP Address, and I tried to connect with another PC using mobile data to use a different network.
My firewall settings are turn off, so I really don't know what is blocking my application to connect to that port. Could it be my ISP is blocking connections? I just don't understand why my ports are blocked even with no firewalls enabled.
Let's assume I'm in computer A, I have a few servers running on different ports, but all are basically an instance of the same program (just binding to different ports). Now, computer B, a client, does he need to know what port is the software he wishes to connect to on computer A?
The point is, I am implementing some sort of communication similar to sockets. Everything should work fine but I'm not sure how to create the initial-message from a computer to another - I just don't know to what port to send it to. Does the client know the port he's sending to on the server?
Say here (client): clientsocket.connect(('localhost', 8089)), does the client connect a server running on port 8089? If so, what port is his socket on (what port is he using for the client?
Yes. The only way for the network stack on computer A to know which process to deliver an incoming packet is for computer B to set the correct port in the packet. A web server runs on port 80 by default, but a machine running several distinct web servers will run them on distinct ports, and a client must be specific about which server they want to connect to. http://example.com, http://example.com:8080, and http://example.com:12345 would refer to the servers running on example.com on ports 80, 8080, and 12345, respectively.
In order to know which port to use in your client, you need to read the documentation for the server you want to connect to.
Going in the other direction, the port used by the client to receive responses is typically set by the networking stack automatically. The client doesn't need to do anything special to set it, and the server simply sends packets back to the address/port found in the source portion of the incoming packet.
I have a question about network connections among computers.
I've made some applications where messages pass through the Internet (via sockets) to make a connection between two devices. However, a strong condition is that two devices must be connected to the same network.
Can anyone give me a trick how to create a communication using sockets between two computers even if they are connected to different netwkorks?
Thank you in advance.
Here is a great tutorial on how to use sockets and general networking
(in java) http://www.thenewboston.org/watch.php?cat=25&number=38
In order to communicate between two diffrent networks over the internet, you will need to do something called port forwarding. What that does is that when your public IP of your network receives a packet with a spesific port number. The router knows where to send that packet to which local IP.
If you dont port forward and receive some data. The router doesent know where to send the packet. Therefore it discards it, which means others wont be able to connect to you.
You will only need to port forward the network with your server (using the example i linked). How you do that is by logging in to your router, and say that a port which the server uses gets forwarded to the IP of the PC hosting the server.
On the other network (client) you will need to change the IP address of which the client shall connect to. That IP address needs to be your public IP of your server's network. You can find that by connecting to the server's network and go to: http://www.whatsmyip.org/ . Keep in mind that public IP addresses may change over time.
Hope this helped!
-Kad
Do I need to have a server to work with sockets?
Can I directly send packets to other client and receive it without neither of the host being a server?
Yes, you can do this. Even on the very same computer. Just make sure they use the same port and the client tries to connect to localhost. I use this technique on a regular basis to test my networking apps.
Any two computers may talk, but one must be a server and the other the client. They can swap roles and each can be the opposite of the other.
The Client / Server distinction in socket programming isn't as specific as it sounds. Basically it has to do with the way the two machines connect.
The server uses bind, listen, and accept to constantly wait for incoming connections. The client has to know the IP address of the server. This is why URLs and DNS exist, to provide an easy-to-remember name that maps to a server's IP address.
Once the client connect()s and is accept()ed by the server, the differences are pretty much over. The client and server can both send() and recv() bytes whenever they want, and there are no restrictions on the data.
Any computer can be a server. You could have a 386 laptop as a server and a brand new dual-Xeon rack machine as a client.
We have a asp.net 3.5 web application running on a hosting company's web server that's got a very strict firewall setup. The web application communicates with our sql server express 2005 which is on a completely different network.
The problem is that the web applications sends our sql server a random port number to connect to when it connects to our sql server on port 1433. Hence the web application can not connect to our sql server because then they have to open a whole range off port numbers on the firewall which they are not prepared to do.
My question is the following. Can you specify either in your connection string or somewhere in your web.config the port the client sends to sql server to connect back to on?
Thanks
If I'm getting you right, you want to do something that goes against how TCP/IP port handling is supposed to work.
You want the web application to always use the same port when connecting to your SQL server? This would mean you can only have one connection open at any given time, and so only one user at any given time. The client is supposed to communicate with a server from a "random" port. It's the basics of networking. At least how I learned it.
I'm not sure you can even force it to use the same port every time, and even if you can I'd advice against it.
I'd say the problem is the firewall, and not your application. I can understand that the SQL server only wants to speak to the IP address that your site is on, but it shouldn't really care which port the client wants to talk over (something like [website-ip]:* -> [sql-ip]:1433). To me, it seems like who ever set up the firewall has some kind of crazy firewall ideas, but maybe that's just me.
Is it possible that your SQL Server Express is configured to listen on dynamic ports? If the 'TCP Dynamic Ports' value is 0, I think it will be dynamic even if you have a specific port configured. That value should be cleared completely.
You can specify port if you are using TCP/IP.
For ex:
Data Source=190.190.200.100,1433;Network Library=DBMSSOCN;Initial Catalog=myDataBase;User ID=myUsername;Password=myPassword;
where DBMSSOCN=TCP/IP