CrashPlan does its best to try and connect to other computers without much configuration on your part, but sometimes you might need to adjust your firewall settings, especially after a CrashPlan upgrade or an operating system update. Follow this guide step by step to get your computers connected.

In rare cases after an update, some users who made no firewall modifications could experience difficulty connecting to other computers. Following an update, a software firewall might identify the new release as new application. Adjusting the software firewall or enabling port forwarding usually resolves the issue, even if you've never had to do this before.

If you are attempting to set up 2 or more computers to back up to each other (known as peer-to-peer backup), you may need to configure these settings for each computer involved.

Some software firewalls are built into the operating system (e.g. Windows Firewall, SELinux, Apple Firewall) and some are third party applications you install yourself (e.g. Norton Internet Security, Little Snitch, etc.). Things like operating system updates can affect the firewall's behavior.

Firewalls have rules for both incoming and outbound connections, so just because a connection works in one direction doesn't guarantee that it will work in another direction.

Check the software firewall to make sure CrashPlan is allowed both in and out on TCP port 4242. Though most software firewalls allow you to make exceptions for specific programs, we recommend you create an exception for CrashPlan and for port 4242.

Be sure to check the software firewall on both the source and destination computers.

If you are unable to connect following an upgrade and already had a firewall exception for the CrashPlan application, please make sure you add an exception for TCP port 4242. With an application exception, some firewalls may detect that CrashPlan has changed following an update and will then stop allowing connections. A port exception is much more resilient.

If you've checked your software firewalls and CrashPlan still can't connect, you can use telnet to help troubleshoot. If telnet can't connect, it means something on the network is blocking communication and CrashPlan has no way to get through.

Note that we are just using the telnet client to test port connectivity on TCP 4242. We are not trying to create an actual telnet session, so you should be able to run the test even if telnet access (TCP 23) is “blocked” on the computer.

To use telnet, you'll need to know the destination computer's IP address. You can view the IP address from either the source or destination computer's CrashPlan desktop.

• From the source: go to Backup, click the destination computer's name.
• From the destination: go to Backup, click the source computer's name.

There are two IP addresses displayed:

• Internal (displayed first): Use if the computers are on the same network or at the same location
• Public: Use this address if the computers are on different networks or at different locations

Once you have the IP address, open a command prompt on the source computer:

• Windows: Start > Run > Type: cmd.exe
• Mac: Utilities > Terminal

Enter command:

telnet IP_ADDRESS_OF_DESTINATION_COMPUTER 4242

Example:

telnet 54.162.1.10 4242

If telnet can successfully connect, you will see an encrypted connection string (a bunch of unintelligible text). Example:

imac2:~ Renee$ telnet 54.162.1.10 4242
Trying 54.162.1.10…
Connected to 54.162.1.10.
Escape character is '^]'.
??d???t”??Y+???+|???ؑ?d6#?еW?{?????6߉?D!@g?????l?????>?]??b6`ۛ??gÖ²$d?c΋?

If telnet cannot successfully connect, you may see connection refused, no response or some other response. Proceed to step 3.

Focus on getting telnet to connect successfully in one direction to help isolate the issue. Test to see if you can connect from Computer A (source) to Computer B (destination).

1. Check the software firewall on Computer A and run the telnet test from Computer B to Computer A.
2. Try disabling your software firewall and 3rd party security software and test again.
   • If the test passes, then you know you have a configuration issue with your software firewall or security software. Consult your manufacturer documentation on how to configure an exception for CrashPlan on TCP port 4242.
3. With your software firewall or security software still disabled, check the router configuration at Site A. Consult your router manufacturer's documentation to make sure your router is configured properly to allow the incoming connection from Computer B. Test again after making any modifications to the router configuration.

Telnet is not installed by default in Vista. To install Telnet, please follow these instructions:

1. Click Start then select Control Panel.
2. Select Programs and Features.
3. Select Turn Windows features on or off.
4. Select the Telnet Client option.
5. Click OK.

A dialog box will appear to confirm installation. The telnet command should now be available.

If the telnet connection fails, enable port forwarding on your router for incoming connections on TCP port 4242. There is some great information about port forwarding including tutorials for various router makes and models at www.portforward.com.

If the telnet connection succeeds and you still can't connect with CrashPlan, proceed to step 4.

If you have multiple computers running CrashPlan on a single network and you've tried everything up to this point, you may need to assign a unique listener port to each computer and configure port forwarding for each port. A symptom might be that one computer connects properly, but one does not.

Good port choices are between 1024 and 5999. Ports 1023 and below are special and should not be used. Before you set a new port, you can use the netstat command to see if any other programs are using the port you've chosen.

Windows:

netstat -ano

Mac / Linux:

netstat -an

Choose another port if something is already listed under the number you've selected.

Once you find an unused port, you can change the listening port option in CrashPlan: Settings > General > Inbound backup from other computers. Make sure to set up port forwarding for that port as well.

• Hardware Vs. Software Firewall (firewall basics): http://www.lockergnome.com/windows/2008/07/14/hardware-vs-software-firewall/
• Information on Apple's Leopard firewall: http://support.apple.com/kb/HT1810