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1. Click on the Apple symbol at the upper, left-hand corner of the screen.
2. Select System Preferences.
3. Select Sharing under Internet & Network.
4. Start Apple Remote Desktop and set the appropriate privileges for it as detailed at Configuring a Mac OS X 10.6 System to Provide VNC Access.

But when I tried establishing a VNC connection to the system from another system on the same LAN, I could not establish the connection. Yet I could establish a VNC connection when I attempted to do so through an SSH tunnel, which led me to believe that the firewall software running on the eMac was blocking the connection.

I went to Sharing again on the system and selected Apple Remote Desktop and then clicked on the Firewall tab. I clicked on the padlock icon so I could edit the firewall settings. I then saw a message telling me that I couldn't change the settings when I clicked on Edit.

You cannot change the firewall settings for this service.

When you turn on Apple Remote Desktop in the Services pane, you also allow the service access through the firewall on TCP port(s) 3238 and UDP port(s) 3238. To stop access through the firewall you must turn off this service through the Services pane.

I didn't see a reference to the default VNC port of 5900, so I opened a terminal window to check the firewall rules (Applications - Utilities - Terminal) using the ipfw command. The command has to be issued while logged into an account that has administrator access on the system.

Maroon-Apple:~ JDoe$ sudo ipfw list
Password:
02000 allow ip from any to any via lo*
02010 deny ip from 127.0.0.0/8 to any in
02020 deny ip from any to 127.0.0.0/8 in
02030 deny ip from 224.0.0.0/3 to any in
02040 deny tcp from any to 224.0.0.0/3 in
02050 allow tcp from any to any out
02060 allow tcp from any to any established
02065 allow tcp from any to any frag
02070 allow tcp from any to any dst-port 3238 in
02080 allow tcp from any to any dst-port 22 in
02090 allow tcp from any to any dst-port 548 in
02100 allow tcp from any to any dst-port 427 in
02110 allow tcp from any to any dst-port 139 in
02120 allow tcp from any to any dst-port 631 in
02130 allow tcp from any to any dst-port 515 in
12190 deny tcp from any to any
65535 allow ip from any to any

I could see that connections to port 3238 were allowed, but there was no entry for port 5900, though the system was listening on port 5900 as a netstat -an command verified.

Haroon-Apple:~ Jim$ netstat -an | grep 5900
tcp4       0      0  *.5900                 *.*                    LISTEN

To resolve the problem, with the Firewall tab selected under Sharing, I clicked on the New button. I then selected VNC for Port Name, which automatically selected TCP ports 5900-5902 and UDP port 5900.

VNC then appeared in the list of services in the firewall window with a checkmark next to it. When I checked the firewall rules with the ipfw list command, I also saw ports 5900 to 5902 listed.

$ sudo ipfw list
Password:
02000 allow ip from any to any via lo*
02010 deny ip from 127.0.0.0/8 to any in
02020 deny ip from any to 127.0.0.0/8 in
02030 deny ip from 224.0.0.0/3 to any in
02040 deny tcp from any to 224.0.0.0/3 in
02050 allow tcp from any to any out
02060 allow tcp from any to any established
02065 allow tcp from any to any frag
02070 allow tcp from any to any dst-port 3238 in
02080 allow tcp from any to any dst-port 22 in
02090 allow tcp from any to any dst-port 548 in
02100 allow tcp from any to any dst-port 427 in
02110 allow tcp from any to any dst-port 139 in
02120 allow tcp from any to any dst-port 5900-5902 in
02130 allow tcp from any to any dst-port 631 in
02140 allow tcp from any to any dst-port 515 in
12190 deny tcp from any to any
65535 allow ip from any to any

I was then able to successfully connect to the system from another Mac by putting vnc://192.168.0.103 in the address bar of Safari (192.168.0.103 was the address of the system functioning as a VNC server). When prompted for login credentials, I could put in the userid and password of an account on the system functioning as the VNC server and log into it.

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When I used it to connect to a Mac OS X system, I was warned that the connection would not be encrypted.

Unencrypted Connection

This connection will not be encrypted. Your authentication credentials will be transmitted securely, but all subsequent data exchanged while the connection is in progress may be susceptible to interception by third parties.

That's not a significant concern for me when both systems are on a Local Area Network (LAN) I control, but I normally tunnel VNC connections through an SSH connection when connecting over the Internet to ensure transmissions are encrypted.

Chrome OS on a Chromebook contains A Secure Shell (SSH) client application. To access it, hit the Ctrl-Alt-T keys simultaneously, which will open a terminal window as a tab in the Chrome browser. Type ssh at the "crosh>" prompt to access the ssh client.

Welcome to crosh, type 'help' for a list of commands.
crosh> ssh

Within the ssh application, typing help will show you a list of the available commands.

ssh> help
connect - connect
dynamic-forward port - dynamic socks proxy (-D)
forward port:host:port - static port forward (-L)
help - this
host <hostname> - remote hostname
key <file> - sets private key to use (-i)
nocmd - don't execute command (-N)
port <num> - port on remote host (-p)
server-alive-interval <num> - set ServerAliveInterval option
exit - exit ssh subsystem
user <username< - username on remote host
Note that this program can only bind local ports in the range
8000-8999, inclusive.
ssh> 

If you wish to encrypt a Virtual Nework Computing (VNC) connection by tunneling it through an SSH connection, you will need to specify a port from 8000 to 8999 as the port to be used for forwarding the VNC traffic when using SSH under Chrome OS. You can do so using a forward command such as the following:

crosh> ssh
ssh> user JDoe
ssh> host my.example.com
ssh> forward 8000:127.0.0.1:5900
ssh> connect

Then using the RealVNC client for Chrome OS, you can specify 127.0.0.1:8000 or localhost::8000 as the address through which to establish the VNC connection. You could also have used forward 8000:localhost:5900 for the SSH forwarding command. The address 127.0.0.1 is the localhost address and with the port number of 8000 tells VNC to try establishing the VNC connection by connecting to port number 8000 on the system on which VNC is running, i.e., the Chromebook. Because there is an SSH tunnel through that port, SSH will route any traffic to TCP port 8000 through its connection to port 5900 on the remote system.

You will still get the warning from the VNC Viewer about transmissions not being encrypted when you tunnel the traffic through the SSH tunnel, but you no longer have to worry about the warning, since the traffic is going through an encrypted SSH tunnel. The VNC Viewer does not know that its transmissions are going through an encrypted tunnel; it only knows that it isn't performing any encryption.

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I checked Google Drive, but the particular Scratchpad note I had been editing wasn't there. Though Scratchpad had at one time been synchronizing between my Chromebook and Google Drive, it appeared it hadn't done so for quite some time.

I opened the Scratchpad app (version 3.1.0), which opened a new browser tab. On the left-hand side where a list of the notes I had created appeared there was also a "Scratchpad tips and tricks" note. I clicked on it; one of the options that appeared in the note was "Connect your Scratchpad to Google Docs." When I clicked on Connect, I saw that, under Options, "Sync with Google Docs" was set to "Off". I clicked on the option to change it and gave the application access to the Google Docs for my Gmail account. I then saw the option was set to "On". Hopefully, now I will have a copy of my notes on Google Docs should the problem reoccur. I recall once previously being asked what version of a note I wanted, the one stored locally or the one on Google Docs.

Note: you can also get to the setting to change the synchronization option by taking the following steps in the browser:

1. Click on the the "Customize and control Google Chrome" button at the top, right-hand side of the browser window, the one with the 3 short horizontal bars one below the other on it.
2. Click on Settings.
3. Click on Extensions.
4. Click on the Options link under Scratchpad and set the synchronization option.

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