RMI (Internet, LAN, Firewall)

Hello everybody.
In the last view days I solved a lot of problems with my RMI based System... There was the registry problem, the IE problem (no RMI support), the access permission problem and so on...
But now everythiung is working properely. I use the Java Plug-In (JRE), so I don't even mind about Microsoft's Java implementation :-)
The registry is working, the server is working and the applet is working, too.
The problem I had is that I couldn't connect to my RMI server from the Internet... the applet could only connect from a LAN-host. The server is running on 192.168.0.1 and I could only connect from hosts like 192.168.*.*.
So I changed the rmiregistry command line:
"rmiregistry &"
to
"rmiregistry -J-Djava.rmi.server.hostname=myhost.net &"
and the server command line:
"java -Djava.rmi.server.codebase=http://myhost.net/msg/ -Djava.security.policy=server.policy MessageServer &"
to
"java -Djava.rmi.server.codebase=http://myhost.net/msg/ -Djava.security.policy=server.policy -Djava.rmi.server.hostname=myhost.net MessageServer &"
("myhost.net" is just a reference for the real domain name)
Now, I can connect the server from outside (Internet) but if I try to connect from the LAN (192.168.*.*) I get an Exception:
java.security.AccessControlException: access denied (java.net.SocketPermission 192.168.0.1:5099 accept,resolve)
Per haps there is a firewall problem. I connect to the internet unsing the gateway (firewall) 192.168.0.1 (which is also the RMI and webserver) and I opened the port 1099 for RMI (but in the exception above there is always another port, for example 5099, 5100, 5101, 5102, 5103) and it looks as if the applet tries to connect on different ports... first for example 4800, then 4801, 4802 and so on (and I really can't open alle these ports).
What should I try... I'm new to RMI and I don't have much experience in using RMI and handling ports, hosts, codebases etc. Is there a possibility to allow the access to the registry/server from LAN AND Internet or what can I do. Is there a possibility to tell the client/server to connect to a fix port (for example 5099) so I would open this port on my firewall.
Please give me some advice... I would be very grateful.
Thanks a lot.
Greetings
Adrian R.
Switzerland

If you look back through this forum you will find LOTS of discussion about operating through firewalls. A lot of it is problems with callbacks. Ignore it (unless this is the next problem you have to tackle.)
The probelm is about as you guessed: The actual communications from client to server program require a socket, and that's a problem unless you can nail down fixed ports and open them in the firewall. (There is supposed to be an automatic workaround built into RMI to use HTTP tunnelling. This may work - I just have no experience using it.)
One basic technique for solving the problem you posted is to define and set a "socket factory" that will provide fixed addresses for the communications.
As I said, look back through earlier postings.

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RMI Clients behind firewall

When the RMI client behind firewall tries to access the server the following error is thrown up:
java.rmi.ConnectIOException: Exception creating connection to: 10.130.12.128; ne
sted exception is:
java.net.NoRouteToHostException: Operation timed out: no further informa
tion
java.net.NoRouteToHostException: Operation timed out: no further information
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(Unknown S
ource)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(Unknown S
ource)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at RMIFaxServer_Stub.getResult(Unknown Source)
at FaxTest.main(FaxTest.java:51)

your client is behind the firewall but the server you're trying to access has an address 10.x.x.x which says that it too is behind a firewall and not on the Internet, or is the server in a DMZ. It sounds more like a networking issue than a java problem at this point. If the server is on some side of a firewall, you may need a some sort of "permit established" config setting added to the firewall. Just a thought.

RMI through a firewall

Has anybody been able to do this. I have an RMI server that will attach on a non-firewalled machine but won't on the machine I really need it on. Can anyone tell me what needs to be done admistratively or programmactically?
Steve

I looked into RMI over a firewall once.
The port 80 solution, called Http Tunnelling, at the time ( 2 years ago ) required a custom servlet intercepting all the RMI calls, then it forwarded the call on to the actual RMI server..... messy.
In the end I recommened writing an RMI Custom Socket Factory.
Not as hard as it looks, and source is available.
It meant that you could have your own properties file which dictated the ports the RMI used. So you might have something like
rmi_ports=1900-2000
You parse the properties file, and only attempt to open ports in that range.
The firewall will off course have to open that range of ports too.
I never implemented this, but did research it a few years back.
Maybe there's a more up-to-date solution.... maybe not.
But that's my 2 cents ( in Euro not dollars ! )
regards,
Owen
http://java.sun.com/j2se/1.5.0/docs/guide/rmi/socketfactory/index.html

I am getting a message that says download failed because of internet connectivity/ firewall

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Hi,
Please refer to the help document below:
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Can RMI get through firewall?

my java applet will have to communicate with SAP server using JCO
so the applet connects to an RMI server then the RMI server connects to SAP server.
in between applet and RMI server there is a firewall. will RMI get through firewall?

The answer is "maybe". It depends on
o How the service is coded. Probably has to be written to communicate using a fixed port number, rather than randomly assigned. (Most firewalls allow access to only specified ports.)
o Changing the firewall settings.
o Whether or not your server tries to call back the client, and whether the client is also behind a fireall. If these two details are both true, then you are probably dead in the water.
There are HTTP tunelling techniques for getting through firewalls. Haven't used them, but if you look back through this forum you'll probbly find some info.

RMI server behind firewall--must use host as name, not IP

Server is running behind a firewall, which runs such that any machine behind the firewall cannot use the external IP to get back to itself.
That is:
- outside IP = 192.171.20.5 (port forwards 1099 to 192.168.1.5:1099)
- inside IP = 192.168.1.5 (rmi server listens on 1099)
from the machine inside (192.168.1.5), it is IMPOSSIBLE to create a socket to [outside ip](192.171.20.5), port 1099, and expect it to get back to the machine inside--the firewall prohibits this.
I -can- use name-based lookups, such that I can edit the hosts file on the inside box to route (myhost.com to 192.168.1.5). So, if everyone's DNS resolves myhost.com -> 192.171.20.5, then clients anywhere can go to myhost.com:1099 and will be redirected to my internal machine (192.168.1.5:1099).
The problem with this is that the names get translated to IPs and sent back to the client.
Is there a way to keep the names as names, so that both client (using external real-world DNS entries) and server (using local hosts file) can both resolve to the proper IP addresses?
I'm starting server, as follows:
java -Djava.rmi.server.codebase=http://myhost.com/rmi/ -Djava.security.policy=/policypath/policy -Djava.rmi.server.hostname=myhost.com mypkg.myclass
The client connects and gets this message (from a connection exception):
java.rmi.ConnectException: Connection refused to host: 192.168.1.5;

Server is running behind a firewall, which runs such
that any machine behind the firewall cannot use the
external IP to get back to itself.I dont really understand this statement.. Machines behind the firewall referring to the external ip would be going to the gateway, not themselves.. Or do you have an internal AND external ip on the machines behind the firewall? Or are we referring to the gateway machine as an internal machine as well as external?
That is:
- outside IP = 192.171.20.5 (port forwards 1099 to
192.168.1.5:1099)
- inside IP = 192.168.1.5 (rmi server listens on
1099)looks good, what kinda OS/firewall? If we're talking linux/ipchains (or iptables) with ip masquerading, I may be of some use to you...
from the machine inside (192.168.1.5), it is
IMPOSSIBLE to create a socket to [outside
ip](192.171.20.5), port 1099, and expect it to get
back to the machine inside--the firewall prohibits
this.If you're on the internal network, why can't you just go for the internal ip addr? If I'm understanding correctly, you want internal dns requests for myhost.com to resolve to 192.168.1.5, and external dns requests to resolve to 192.171.20.5? That should't be a problem...
I -can- use name-based lookups, such that I can edit
the hosts file on the inside box to route (myhost.com
to 192.168.1.5). So, if everyone's DNS resolves
myhost.com -> 192.171.20.5, then clients anywhere can
go to myhost.com:1099 and will be redirected to my
internal machine (192.168.1.5:1099).the hosts file has nothing to do with routing, it's simply a dns-type thing... If your dns is giving external users a 192.168 address as the ip for myhost.com, they will never get to it. 192.168 is not routable on the internet, i think most inet routes will drop packets from 192.168.x.x or 10.x.x.x.
Is there a way to keep the names as names, so that
both client (using external real-world DNS entries)
and server (using local hosts file) can both resolve
to the proper IP addresses?As long as your dns is working correctly, java doesn't care if you use ips or host names.. Hostnames are preferable, so when you change your network around, you wont affect your rmi server.
I'm starting server, as follows:
java -Djava.rmi.server.codebase=http://myhost.com/rmi/
-Djava.security.policy=/policypath/policy
-Djava.rmi.server.hostname=myhost.com mypkg.myclass
The client connects and gets this message (from a
connection exception):
java.rmi.ConnectException: Connection refused to host:
192.168.1.5;Is your server compiled with the 192.171 ip? That's not gonna work, you have to use the same IP the server is running on. I'm still not clear on your network layout, is 192.171.20.5 and 192.168.1.5 the 2 gateway ip's, or is 192.168.1.5 a physically different machine? I'd be willing to bet that your server is compiled with the external address, and if that's not the same machine, then there's no chance of that working....
There's more than port forwarding going on.. IIRC, java rmi keeps track of its own ip's.. A client request to an external ip will not connect to a server running on the internal ip, even if you forward the port, rmi itself doesn't recognize the internal as the ip it's trying to get to (even if it is true), so it bombs out.. This can happen if you run the rmi server on a gateway, and compile the server with the external ip, and try to connect to the internal ip.. If you want external machines to connect, you MUST run the server on an external ip.
Give a little more info, we'll getcha running... I'm also assuming you have full control of your network (ie, firewall/dns)
doug

Strange: just lost use of Built In Internet (LAN) connection!

Greetings,
I was just switching from wireless Airport connection to Built In internet (wired/LAN) connection (I do that to insure more reliable large downloads, software updates), and I realized that upon Turning Off Airport, I was not getting automatic connection to the built in NIC, as I do usually. I checked Preferences >>> Network, and observed that the built in connection was "inactive". I am not sure how to activate it again. LAN cable is OK, internet connection and modem OK, etc...
I'll appreciate refresher!
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sig, thanks a lot for your prompt reply... I had restarted the system indeed.
I got to start looking deeper into seldom visited settings... And I found one that fixed the problem.
I went to "System Preferences" >>> "Network" >>> observed that the "Built In Internet" was INACTIVE >>> clicked on the smal, gear-like button at the bottom, right next to the "+" and "-" buttons. AND, lo and behold, by making the "Service Active", I restored the Built In Internet" connection.
Man, go figure what disconnected it in the first place! I just drew a blank initially!
Thanks again... Sometimes, one needs a prod
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I've checked the forums here and this exact problem isn't jumping out at me.
6 months or so ago I replaced my router with a Time Capsule. Everything worked fine for months and months. We had a power outage (I have battery backup UPC) several weeks ago and when the power came back my G5 and my wife's iMac (both Ethernet LAN connected) had lost their LAN DHCP address (192.168.0.x) and were self-assigning their own IP's. The WiFi connection had internet access and after restarting a gigabit ethernet switch on the LAN everything came back.
For weeks everything was fine. Yesterday after coming home from work my G5 had lost it's DHCP address and internet connectivity. I've tried resetting/restarting everything (hardware and network connections). Here are weird particulars :
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Thanks so much, I'm dead in the water on the desktop.
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Thanks Glen. I tried renew the lease. It never got a lease in the first place. Also tried resetting PRAM and Safe Mode boot. No luck on auto DHCP for this machine.
I do get internet and LAN connectivity if I switch to manual DHCP (I found it's necessary to enter the router address, 192.168.0.1 or it doesn't work).
So now it's working (on Manual) but it bothers me that I can't pick up a LAN IP from the Time Capsule (on Automatic) like it did everyday for a long time. No software changes were made, just Repair Permissions (Check Disk showed no problems). It's a weird problem as all other appliances (computers, iPhone, ATV, etc) are working fine. Just the G5 (same cable, same everything as far as I know).
Thanks,
Ed

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I'm having a strange problem getting RMI HTTP Tunnelling to work with a firewall installed. I configured my code to use HTTP Tunnelling a few months ago, and had no major issues. Now that we have begun testing in the production environment with the real firewall, I am getting several errors.
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java.rmi.NoSuchObjectException: no such object in table
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Sorry, that's not correct. I have done some more testing, and it looks like the lookup works, but when I actually try to use it, the call fails.
I was able to open up the port that RMI uses, and I get the same problem. Perhaps the issue is with the port that the object uses: 58494. I'll check with our network guy.

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What port should be opened to let rmi traffic passing through firewall to weblogic app server?

Dahan <[email protected]> writes:
What port should be opened to let rmi traffic passing through firewall to weblogic app server?The port the server is listening on?
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ello guys i want to hit 3 birds with one stone
Anyhow here it goes
I need a internet connection and lanline ability to call via wireless as i have no phone line in my new unit for another 5 months.
As far as visible solution with no contract
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Up!

RMI (Internet, LAN, Firewall)

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