I am programming a server system for a small RPG game made with SFML. This is my first project since we switched our ISP to Comcast and I am having trouble with people connecting to the server. I can connect locally fine and all of the port checking tools say that the port is open, but my friends cannot connect using my external IP. I turned my firewall off on my router and on my computer to see if it'd help the situation at all, but the same thing is occurring.
Comcast gave me an Arris TG862G-CT router.
Here's an image of the port forwarding page:
The port is shown as open, but my client cannot connect:
I'm not sure which language you are using, but many make a distinction between opening a port with the host address 127.0.0.1, 0.0.0.0, and localhost. Many times you will need to use 0.0.0.0 to connect from an external pc where as 127.0.0.1 and localhost are used as a loopback and only accessible by you.
Related
Adding an inbound Windows Firewall rule (via COM from C++) for local port 80 and addresses ANY, 127.0.0.1 or 0.0.0.0 does not block a local browser from accessing a local web server running on port 80. For debugging/testing purposes, I need to simulate loss of network connectivity between two programs running on the same computer. Is there a way to do this programmatically, on the command line, or with a tool?
In this question, they say allegedly there is no way to do this in the Windows Firewall:
How do I block localhost connections with the Windows 7/2008R2 firewall?
Is there a way, other than Windows Firewall, just to simulate loss of network connectivity between programs running on the same computer?
There is WIPFW -- a Windows port of FreeBSD's IPFW. However, I failed to get it to block localhost connections. Maybe you'll have more luck.
Alternatively, you can try a hack. If your programs establish a connection using the localhost host name instead of directly by the 127.0.0.1 IP address, you may change your hosts file to point the localhost name to some non-existing or otherwise unreachable address.
I'm writing a program on Windows using winsocks that can send messages to another computer. The client connects with the server in the other computer and begin exchanging data.
It works fine on my local network using local addresses(192.168.1.*), but I can't communicate with public addresses (216.185.45.129); not even my own. I can successfully connect to a website on port 80, but not to my laptop at home using its public IP address, regardless of what ports I use (unreserved ports).
So I did research online and the only solution that seems to work is port forwarding.
-But is there absolutely no other way to achieve this?
-How do other programs like Teamviewer connect to other computers on the network then?
-Is there an already open but typically unused port that I can use?
-At the very least, can I forward the ports on my router but not have the client do anything? Or maybe have my program forward the ports automatically.
The main problem is, that every router is using NAT to distinguish different computer in your lokal network against the WAN. He need to do this, because you got only one IP in the internet, but several devices in your home. To archive this, he uses groups of ports. That means, if you use to send maybe from port 2048 to a webserver in internet with two devices, the router gives one device another port (like 2049). The response has the Port of the requester, so the router can map it back. Unfortunately most router always map ports so you never now which port you have from the internet side.
There are two common ways to work around and archive your goal.
Port Fowarding
You can force most router not to map special ports but bind them to unique MAC addresses. You can use UPNP to config most router to do that, but I do not recommend that for security reasons and also it does not work in many enviroments where Router do not allow UPNP manipulation.
Most router have port forwarding abilities for gaming reasons (mostly it is used in P2P networks)
It works with TCP and UDP.
NAT Traversal
The common way is NAT traversal, also known as NAT hole punching. I will describe it in short for UDP. You can find a wiki explanation here for TCP and for UDP here. Unfortunately you need a server in the internet both clients can reach. Here the steps:
Both clients contact the server. The server now know IP and PORT of both clients.
Server send back the information to the clients.
Both(!) clients send now packages to each other on the known address.
It is necessary that both client send a UDP package and have to accept that the first package get lost. The reason is the router. Most router only accept packages from a source on a mapped PORT if a client has send a package to that source before.
UPDATE
Regarding to a comment of Remy Lebau I changed the Firewall piercing part to NAT Traversal as it was partly wrong.
I've got a problem in socket programming. I'm currently writing a simple server/client application which asks connecting clients to answer a survey (I'm following the exercises in the book: TCP/IP Sockets in C: Practical guide for Programmers). It works fine in my local network (using localhost to connect), but I can't make it work over the internet.
Since I changed some of the code found in the book, I tried to compile the original source code from the book but it still doesn't work. I assume this is not a code problem but a network problem.
I did some research and so I turned off my firewall, I forwarded the port I'm using (12543) in my router but it still doesn't work... I've got a remote windows server running Windows 7 for testing: when I run my server on it and try to connect from my computer it fails, when I try to run my server from my computer and try to connect from the remote windows server: it fails again. Even when I run my server on my computer and try to connect with the client from the same computer using my private IPv4 address 192.168.x.x or my public one, it fails ! Oh, and there is no firewall running on the windows server.
I really don't know what to do now... I can ping my windows server from my computer, I can ping my computer from my windows server, but it's impossible to connect to my application.
The source code can be found here: http://cs.ecs.baylor.edu/~donahoo/practical/CSockets2/textcode.html (SurveyServer2.cpp, SurveyClient2.cpp, SurveyCommon.h), but I don't think it's a code problem.
Please tell me if it's not clear enough. And excuse me if I did some grammatical errors, I'm french!
Any help would be appreciated, thanks!
EDIT : Ok, I know what's going on: it's a compatibility issue between IPv4 and IPv6! It's not properly working yet, but I now know what to fix. Thanks everybody :)
SECOND EDIT : Well, I think I finally understood. I was binding my server to a IPv6 address, but the host my server is running on only have a public IPv4 address. When I tried to connect, the DNS resolution only returned a IPv4 address so I was unable to connect to my server. I told to getaddrinfo to return only IPv4 addresses, so now it binds on a IPv4 address and it works fine.
There is surely a way to add a IPv6 address to my host but I don't think I will need it, it works okay right now, I hope this doesn't cause any trouble.
The code makes usage of getaddrinfo and need a hostname not a IP address.
It does sound like you have a connectivity issue or a DNS issue.
Ensure the name resolution is working:
Enter 'ping server_NAME' on the command line of the client machine.
If it can't find an IP address for the server name that could be your issue.
Ensure connectivity:
On the server command line:
enter 'netstat -an -p TCP'. This will show a list of all programs listening and their port numbers. You should see your server listening on port 12543.
On the machine where you are running your client program:
Use telnet to see if you can get through to the server. You can set the port number telnet uses with a command line option. Usually something like 'telnet -p 12543 server-ip'. If it says 'connection refused' then there's a connectivity issue (a firewall/etc). If it opens a connection you will get no error message and you will be able to type text to be sent to the server. You really only care if telnet was able to establish a tcp connection here.
If Telnet does connect then your issue is communication between the programs and not a network issue.
I have written a client/server code.
The server program executes on a terminal which plainly receives text data from the client and the client is a GUI where in you could specify the IP address of the machine where the server would be running.
However this works only in a closed Network(LAN).
I have just learnt TCP IP and have written a few codes that run on a LAN.
I wanted to make this program work across the network(over the internet).
But I have some basic doubts like,does one need the permission of the local ISP for such programs to execute across the internet.Does it involve buying a domain or some kind of permissions?
Can some one please help me on,what should I be doing,or where should I start from?
Listener have to have IP port opened in some way. If you are behind router, you should set proper port forwarding on router and if ISP provides its own subnet, you should know how to setup such link. (i do not know what kind of tehnology ISP might use for this).
For beginning you do not need you own domain name but you should be able to address by ip. If you need domain, register own domain name or create subdomain for free (i was using http://freedns.afraid.org/ )
If your server is behind a router which creates a LAN, you have to configure the router that it will forward the packages from your client to the server.
You have to forward all the incoming packages at the specific port to the local ip of the server.
I have a C++ Program listening for incoming socket connections on port 2222.
I have an Adobe AIR/Flex application that attempts to connect to it, when I click a button.
When I Connect To My Socket Over My Intranet, My C++ program hears and accepts the incoming socket connection and Everything Works Fine:
var Sock:Socket=new Socket("192.168.1.100",2222);
But When I Try To Connect Using My Real IP, I Get Error #2031:
var Sock:Socket=new Socket("76.18.24.118",2222);
Both programs are running on my laptop computer. I am behind a router, but have configured that router with port forwarding so that port 2222 maps to my laptop.
What Am I Missing? I am very new to this, so perhaps I'm missing something obvious to you smarties.
What does the error code mean (see your docs for socket)
Are you sure the receiving server process is alive?
The traditional starting point is Beej's guide
Port forwarding does not mean that you can use an external IP address, your laptop is still on the private 192.168 network. What it means is that when someone tries to connect on 78.18.24.118:2222 the router converts the IP address to 192.168.1.100:2222. This effectively allows you to run a server inside your network but allows an outside client to connect to you.
Look up DNAT for more information.