I am trying to tcp connect to a server machine in java, by using its public i.p. but when i run the client application i constantly getting a connection refused error. if i used localhost instead of the public ip, it works perfectly.
i search the internet for several causes of the issue but i couldnt fix it.
i forwarded the port to my machines' local i.p address(192.168.1.3) in routers settings. then i checked if port is listening when i ran the server application using netstat -an. i saw lines like,
0.0.0.0:19999 or []:19999 .
19999 is the port number i am trying to listen to. Then i changed my ServerSocket constructor to the 3 parameter one, which also binds the local address.
InetAddress miad = InetAddress.getByAddress(addr);
ServerSocket socket1 = new ServerSocket(port,10,miad);
addr is the InetAddress of my machines local i.p. After these modifications, when i start the server application, i run netstat and it shows:
TCP 192.168.1.3:19999 0.0.0.0 LISTENING
Here i think that my server is listening on the port specified properly.
I have also disabled my firewall and antivirus software.
I have seen several threads and discussions on the net about the issue, and tried most of the things mentioned there, but i keep getting the connection refused error.
What can i be doing wrong? It runs without any errors when i test with localhost.
This is because of the router (not very sure, but almost). Try to see if a webservice like www.canyouseeme.org can connect to your server.
The main idea is that an internal machine (inside the LAN) cannot connect to a machine inside the same LAN by using the external (public) IP address.
I'm pretty sure that it will work, using you internal ip (192.168.1.3).
And if you are sure that you forwarded ports correctly, CanYouSeeMe will say your server is reachable. If it doesn't, make sure you ISP isn't blocking the ports for some kind of "safety reasons".
To figure out if your problem relates to Java and programming please do
telnet 192.168.1.3 19999
If it can't connect then superuser.com would be a better place to discuss this issue.
Related
I created and debugged a simple net application that uses AsynchronousSocketChannel and AsynchronousServerSocketChannel and they work fine when accessed via localhost, but even if I move the server application to another device it refuses to connect at all. I first noticed this when I tried to port-forward the application, but upon moving it onto a device on the same network and connecting via the IPv4 it still didn't work. I checked both devices and they both are allowing Java through the firewall and there is nothing blocking the port number I am using (I have also tested various other ports). The client can't even connect to the server if it's on the same machine and you use that machine's IPv4. It literally only works on localhost. Has anyone else ever had this issue?
This is how the server channel is opened:
serverSocket = AsynchronousServerSocketChannel.open();
serverSocket.bind(new InetSocketAddress("127.0.0.1", port));
Fixed it by removing the IP part of the InetSocketAddress:
serverSocket = AsynchronousServerSocketChannel.open();
serverSocket.bind(new InetSocketAddress(port));
Replacing 127.0.0.1 with the IPv4 of the machine has the same effect. If someone could explain this that would be great, because every example I've seen online has binded to localhost. Are AsynchronousServerSocketChannels not supposed to be accessed remotely or something?
I have developed a Chat Application for two person, one being server another will be client, using Java Socket Programming. Every thing was fine till this morning. It was working over localhost, local networks as well as On my DDNS ( My Router is configured to forward any traffic on it's port 8888 and 3434 to same port on my IP, which is again Reserved in my router ). But now it works strangely. I ran a server on my laptop at port 8888 I tried to connect the client through my DDNS on port 8888, Client shows it is connected, but Server shows it is disconnected. Client even sends message successfully which does not appear in server.
I want to know what causes such strange behaviour of my application, is this my firewall, because I have used my DDNS a lot in order to debug some issue.
I also want to know what precautions should one take in order to use DDNS in Java Socket.
Additional Informations:
My DDNS in on Dynu
OS: Windows 7 32 bit
Quick Heal Antivirus and firewall (Outdated)
I am adding some pictures:
Im using TCP/IP sockets in java to try and create a client-server application. The program works fine when run locally and also over the local area network, but when I use the internet IP address the clients connection is refused.
I used this website to get my IP address and have added a firewall entry to unblock the port im using (port 4445).
I am almost certain the problem lies in some sort of security measure that is blocking the port. Does it matter that I'm running the client and server on the same PC but using the IP address from the previously mentioned website?
If I could get a list of ways to test the port is in fact open, or a list of things to try in order to get my program running, that would be great!
That website may very likely give you the IP address of the gateway through which your PC is connecting to the internet, and if the gateway is out of your control (which is most of the cases as far as I know) there's nothing you can do to use that IP address to test your program. Here's some advice:
Try http://aws.amazon.com, once registered you have one-year free access to a micro-server (which can be accessed publicly through DNS/Elastic IP.)
If your PC have a public IP address, you don't need that website to find out what it is. Just check your network adapter control panel.
Where is the server has been located? If your server is located in some commercial hosting, there is possibility that the ports you use are blocked. Also if you use modem with router or just router in your local network you should check nat table.
I have a play application connecting to a database at 1.2.3.4 but for some reason Play! (and other java apps too) cannot connect to it.
I did try editing the hosts file and setting a name for the IP like app01 1.2.3.4 however it only worked on the box where the DB was hosted and it didn't work for external machines. I can confirm that the right port is open in iptables and I've tried restarting it, too.
If I ping postgres at port 4567 at 1.2.3.4 from the same box, it works. But setting the same IP address in my java apps fail. What's wrong? Is it permissions or iptables issue? Thanks.
Stack trace:
Caused by: java.net.NoRouteToHostException: No route to host
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:327)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:193)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:180)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:384)
at java.net.Socket.connect(Socket.java:546)
at java.net.Socket.connect(Socket.java:495)
at java.net.Socket.<init>(Socket.java:392)
at java.net.Socket.<init>(Socket.java:206)
at org.postgresql.core.PGStream.<init>(PGStream.java:62)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:76)
... 35 more
Can you connect to your DB via pgadmin (http://www.pgadmin.org/)?
Can you telnet from your machine on to the DB Server on the given port (telnet 1.2.3.4 4567)?
If you cannot telnet maybe the DB Server is blocking your connections?
Have you set any proxy server either only for java or only for rest of the system?
From the exception it seems more of a networking issue than anything with java...
Can you check firewall settings on the db server. You can try by telnet to check whether you are able to connect or not.
If you're behind a router you WILL BE ABLE to ping it from another local machine (usin the local IP), but you might not be able to ping from the outside if you are not port-forwarding correctly (You can configure this from your router).
Another thing to take in mind is that you CAN'T ping your own external IP from within the network, that means that you can ping 192.168.1.100 (Server) from 192.168.1.xx (Client), but you can't ping 72.15.xx.xx (port-forwarded to 192.168.1.100) from 192.168.1.xx (Client).
In order to do this you have to use an external tool, there are many webs that can do this for you, here's the one that I use:
http://www.yougetsignal.com/tools/open-ports/
If it says the port is open then it is open and it should work now, if it shows closed then you should double check that your firewall is allowing the data, maybe shut it down temporary to see it thats the prob.
If you need help adding a port exception to your firewall or forwarding a port from your router just tell me which distro/routerModel you're using and I'll try to dig some more info for you.
I made this program:
http://java.sun.com/docs/books/tutorial/networking/sockets/clientServer.html
And it works perfectly if I put the server's hostname as 127.0.0.1 or my computers name (Ajay-PC).
However these 2 methods are LAN or local only not internet. So I changed it to my internet ip. 70.128.xxx.xxx etc. But it didn't work. I checked:
canyouseeme.org
and it said 4444 was CLOSED.
So I did a quick port forward.
Portforward:
Name: My Java Program
Start Port: 4444
End Port: 4444
Server IP: 10.0.0.12 <-- (Yeah this is my Local IP I checked)
then I tried
canyouseeme.org
AGAIN:
and it said 4444 was OPEN
I ran my server client program and it yet to work.
So my problem is the client server program is not working on the internet just locally. So something is blocking it and I don't know what.
EDIT: It's not blocked because as I checked the port is open. But I am recieveing a IO exception not a UnknownHost
Computer:
Windows Vista x64
Norton AntiVirus 2010
Thanks! I'll give best answer or whatever to who ever answers the best ;) :)
How do you have access to the internet? Maybe you have to configure your ADSL modem or your router/switch to forward the port 4444 to your computer.
I guess you are in the LAN if you are using a router connecting to your modem. And your computer connect to the router.
Try to connect to your modem which has your internet IP.
Have you checked that the client is connecting to port 4444 and your public IP? This is another common mistake most people make. If your port is open as you say above and the firewall is off, then there's nothing stopping you connecting.
Use Wireshark or WinDump to snoop the initial TCP handshake. Filter for packets with port 4444. Verify that the opening SYN packet is leaving your computer, that the opening SYN packet is returning to your computer, and to see what whether/how computer is responding to the opening SYN packet.
Note: if you experiment with these tools, you won't be able to use it trace if you use the localhost (127.0.0.1) and your PC IP (10.0.0.12) addresses - in these cases, the packets don't actually leave the computer and can't be snooped. Put the client and server on separate computers if you want to snoop packets on the LAN without involving the gateway.