View source for NAOS v1.1.4.x

{{na_v1.1.4_header}}

NAOS: Node Assassin Operating System, is the software that controls the Node Assassin cluster fence device. You '''must''' modify it to fit your network before you load it into your device.

= Release =

* Last update: Apr. 13, 2010
* Tested using IDE: Arduino Alpha v0018 (x86 and i386)
* NAOS Version: 1.1.4.4

= Notes =

'''Apr. 13, 2010''': Released v1.1.4.4

To upload NAOS, you will need to use the [http://arduino.cc/en/Main/Software Arduino IDE].

== WARNING ==

'''''USE THIS CODE AT YOUR OWN RISK!'''''

It's the default warning for everything related to this project, but it's worth repeating here. This code comes with no guarantee in any way, shape or form. This has only been tested on my Node Assassins. Specifically, it's been loaded on the Arduino Duemilanove with the ATmega320 chip connected to the Wiznet W5100 ethernet shield. I can't guarantee it will work on any other hardware, but I would love to hear from you if you do try it elsewhere!

== Changes To Make BEFORE Uploading ==

Before you upload NAOS to your Node Assassin, be sure to modify the following variables to suit your device and environment. The variables listed below are critical to check, but there other optional variables you may want to change such as the device name, serial number and so on. The source code is heavily commented and you can find details on safe and sane edits in the top part of the source code.

* Change the network address to fit your network. The defaults are:
{|style="border-left: 1px dotted #7f7f7f; border-top: 1px dotted #7f7f7f;"
|-
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;"|''Type''
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;"|''Default Value''
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;"|''NAOS Variable Name''
|-
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f; font-weight: bold;"|MAC Address:
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|02:00:00:FF:F0:AA
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|byte mac[] = { 0x02, 0x00, 0x00, 0xFF, 0xF0, 0xAA };
|-
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f; font-weight: bold;"|IP Address:
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|192.168.1.66
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|byte ip[] = { 192, 168, 1, 66 };
|-
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f; font-weight: bold;"|Netmask:
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|255.255.255.0
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|byte nm[] = { 255, 255, 255, 0 };
|-
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f; font-weight: bold;"|Gateway:
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|192.168.1.1
|style="border-right: 1px dotted #7f7f7f; border-bottom: 1px dotted #7f7f7f;" class="code"|byte dg[] = { 192, 168, 1, 1 };
|}

== Thanks ==

The majority of this first version was made possible thanks the generous patience of Mark Loit at [http://hacklab.to hacklab.to] who spent the day giving me a crash course in C and helping me diagnose my first circuit. He also gets the credit for the project's tag line.

= Code =

* [http://nodeassassin.org/files/naos/naos-1.1.4.4.c Download] v1.1.4.4 source.

<source lang="c">
#include <Ethernet.h>	// Arduino's ethernet library.
#include <ctype.h>	// Library for testing and character manipulation.
#include <stdint.h>	// Library for standard integer types (guarantees the size of an int).
#include <stdlib.h>	// Library for things like 'sizeof()' and 'itoa()'.

// IMPORTANT NOTE!
//   Be sure to update the IP Address, Subnet Mask, Default Gateway, MAC
//   address and serial number before loading this software into your Node
//   Assassin!

/*
Author:
 - Digimer
 
Version: 1.1.4.4
 - Release: Apr. 13, 2010

License:
 - The GNU GPL v2.0

Thanks:
 - Hacklab.TO:       The idea for this device was born there.
 - Christopher Olah: Came up with the name "Node Assassin".
 - Mark Loit:        Taught me enough C to write version 1.0 of NAOS!

Bugs:
 - None known at this time.

Protocol:
 - Telnet (or similar) to the IP and Port set below.
  - To query the state of the nodes, send:
    - 00:0
  - To query the Node Assassin's details, send:
    - 00:1
  - The integer after the '00:' is reserved for future queries.
 - To set the state of a node, send:
  - XX:Y
  - XX is the zero-padded node ID number; 01, 02, 03 or 04
  - Y  is the state to set
    - 0 releases the fence and lets the node boot.
    - 1 fences the requested node.
    - 2 Fence for one second. Useful for rebooting a node or for when a port
        is connected to a node's power button to boot or gracefully power down
        a node (via ACPI).
    - 3 Fence for five seconds. Only useful when connected to a power button.
        This allows the Node Assassin to force a frozen server to power off.
 - Example:
   - To fence Node 01, send:
     - 01:1
   - To release the fence and thus let the node boot, send:
     - 01:0
 - Sending any other non-standard command will generate an error message and no
   action will be taken.
  
Note:
 - This device implements NO security. You MUST install it on a private, secure
   intranet or similar back channel. Installing it on the same LAN as the
   storage devices is advised. 
 - Changing this file will have no effect until the program is recompiled and
   uploaded to the Node Assassin.
   
To Do:
 - Make naming the device and setting its network settings configurable.

Changes:
 - v1.1.4.4
   - Fixed a bug where the node being worked on was displaying as one higher.
 - v1.1.4.3
   - Increased the 'osVersion[]' array to length ten to properly store and show
     longer version numbers.
 - v1.1.4.2
   - Updated/Cleaned up the comments in the code.
   - Changed the prefix for bad commands from 'ERR' to 'ERROR'.
 - v1.1.4.1
   - Fixed the numbering of Nodes in '00:0' status requests.
 - v1.1.4
   - Changed the version number to correspond to the matching supported Node
     Assassin hardware version.
   - Added the concept of "nodes" which are groups of two digital outputs plus
     one analog input treated as a digital input.
   - Changed the states. Most critically, 0 now releases the fence and 1 fences
     the node. Further, "fencing" is no longer simply closing the switch. A
     fence triggers a sequence of switch open and closing to accomplish the
     fence.
   - Added support for node feed detection and added errors and warnings to
     state calls that are based on the feed values.

 - v1.0.4
   - Set all output to send a final 'EOM' (End Of Message) on a new line after
     all output for the fence agent to know when data has finished returning.
   - Prefixed all error messages with 'ERR: '.
   
 - v1.0.3
   - Added the '00:1' query message which returns the Node Assassin's details
     and identification.
   - Added the '##:2' and '##:3' options.
   
 - v1.0.2
   - First release.
*/

// MAC Address; Array of six bytes.
// If you've been assigned a MAC address by AN!, or if you have your own block
// of MAC addresses, enter it here.
// NOTE! If you do not have a MAC address, choose one that starts with 0x02.
//       This will mark it as a locally administered MAC address. For example,
//       use "{ 0x02, 0x00, 0x00, 0xFF, 0xF0, 0xAA }".
byte mac[] = { 0x02, 0x00, 0x00, 0xFF, 0xF0, 0xAA };

// Arduino IP, netmask and gateway.
byte ip[] = { 192, 168, 1, 66 };

// Netmask defaults to 255.255.255.0.
byte nm[] = { 255, 255, 255, 0 };

// Default gateway defaults to IP with the last octal set to 1.
byte dg[] = { 192, 168, 1, 1 };

// The user-set name of the node, up to sixteen characters long.
char nodeName[16]="Motoko";

// The serial number.
// NOTE! Only set a serial number starting with 'NA####' if you were assigned
//       one by AN!. Otherwise, use 'PR####' where the digit section is your
//       internal tracking number.
char serialNumber[7]="PR0001";
char osVersion[10]="v1.1.4.4";
// The buildDate variable represents the date that the Node Assassin you are
// using was built.
char buildDate[11]="2010-04-03";

// This is the port that I will listen on.
#define PORT 238

// Setup the server.
Server server = Server(PORT);

// Setup my digital out pins.
// CONSTRAINT: Input and Output pins must be assigned sequentially
#define NODECOUNT      4
// The digital pins are output
#define FIRSTOUTPIN    2
// The analog pins are treated as digital inputs, so I count them from 14 - 19.
#define FIRSTINPIN     14

// My function prototypes.
void printError(const char *message);
void printMessage(const char *message);

// Setup the Arduino on boot.
void setup()
{
	// Setup the IP info.
	Ethernet.begin(mac, ip, dg, nm);
	
	// Print the serial port welcome message.
	Serial.begin(9600);
	Serial.print("Node Assassin: ["); Serial.print(nodeName); Serial.println("] starting.");
	
	// Iterator to setup the digital pins to output and to set them
	// initially to LOW.
	for (int pin = FIRSTOUTPIN; pin < (FIRSTOUTPIN+(NODECOUNT*2)); pin++)
	{
		Serial.print("Set - pin: ["); Serial.print(pin); Serial.println("] to OUTPUT/LOW.");
		pinMode(pin, OUTPUT);
		digitalWrite(pin, LOW);
	}
	
	// Iterator to setup the analog pins as digital inputs.
	for (int pin = FIRSTINPIN; pin < (FIRSTINPIN+NODECOUNT); pin++)
	{
		Serial.print("Set - pin: ["); Serial.print(pin); Serial.println("] to INPUT.");
		pinMode(pin, INPUT);
	}
	Serial.println("Ready!");
	
	// Start the server listening for connections.
	server.begin();
}

// And GO!
void loop()
{	
	// Variables
	uint8_t node=0;		// Node to work on, if applicable.
	uint8_t state=0;	// The state to set the node(s) to.
	int node_power_pin=0;	// This will contain the actual pin mapped to
				// the requested node's power pin (digital pin).
	uint8_t np_state;	// This will contain the power state.
	int node_reset_pin=0;	// This will contain the actual pin mapped to
				// the requested node's reset pin (digital pin).
	uint8_t nr_state;	// This will contain the reset state.
	int node_feed_pin=0;	// This will contain the actual pin mapped to
				// the requested node's feed pin (analog pin).
	uint8_t nf_state;	// This will contain the feed state.
	char nodeASCII[3];	// ASCII representation of node number. This is
				// '3' because of 'first char' + 'second char'
				// + terminating <NUL>
	char command[5];	// 5 chars "XX:Y" + <NUL>
	int  index = 0;		// An index to increment and reset in loops.
	char macString[6];	// MAC address.
	
	// Start the network library.
	Client client=server.available();
	if (client)
	{
		// process the input in a line-based manner, allowing for 1
		// command per line
		while ((-1 != (command[index] = client.read()) ) && (5 > index))
		{
			// exit at the end of line
			if (('\n' == command[index]) || ('\r' == command[index]) )
			{
				break; // EOL found, break out of the loop.
			}
			index++; // advance the index.
		}
		// on a valid line the above loop will exit with index == 4
		
		// If there is no message, nothing to do but exit. 
		// Coding note: By putting 0 first, I can never accidentally
		// set the variable to '0' with an accidental single-equal.
		if (0 == index)
		{
			return;
		}
		
		// sanity check on length
		if (4 > index)
		{
			printMessage("ERROR: Message too short.\n");
			printMessage("EOM\n");
			return;
		}
		
		// Spool off whatever is left in the buffer/line in case it was a string longer than 4.
		if (5 == index)
		{
			char ch;
			printMessage("ERROR: Message too long.\n");
			printMessage("EOM\n");
			while (-1 != (ch = client.read()) )
			{
				// exit at the end of line
				if( ('\n' == ch) || ('\r' == ch) )
				{
					break; // break out of the loop.
				}
			}
			return;
		}
		
		// <NUL> terminate the string
		command[index] = 0;
		
		// Parse the string; Error if anything isn't right.
		// Make sure we have a colon in the right location
		if (':' != command[2])
		{
			// Error
			printError(command);
			return;
		}
		// Make sure the other characters are digits
		if (!isdigit(command[0]) || !isdigit(command[1]) || !isdigit(command[3]))
		{
			// Error
			printError(command);
			return;
		}
		
		// No need to check for the terminator or newline at the end,
		// that was taken care of in the read loop.
		// Do the math to turn the ASCII node number into a binary
		// value.
		node=command[0]-'0';	// First digit convertion (ie: '1'
					// (0x31)-'0' (0x30) = 0x01 = 
					// "0000 0001 (dec. 1)").
		node*=10;		// Shift to the first base-10 position.
		node+=command[1]-'0';	// Now 'node' contains the binary
					// version of the ASCII two-digit value
					// read off of telnet.
		
		// Convert the "node" value to the actual power and reset pins.
		// Because each node consumes two digital output pins, I need
		// to double the 'node' value and then add the digital out
		// offset. This will give me the reset pin directly, and then
		// subtract by one to get the power button pin. The Feed pin is
		// simple the node's value plus the input offset less one.
		node_power_pin=(((node*2)-1)+(FIRSTOUTPIN-1));
		node_reset_pin=((node*2)+(FIRSTOUTPIN-1));
		node_feed_pin=(node+(FIRSTINPIN-1));
		
		// Do the math to turn the state number into a binary value.
		state=command[3]-'0';	// Now 'state' contains the binary
					// version.
		
		// copy the ASCII node name for the response messages so that
		// we don't have to convert it back later.
		nodeASCII[0] = command[0];
		nodeASCII[1] = command[1];
		nodeASCII[2] = 0; // <NUL> terminate it
		
		// Make sure the requested node is actually available on this
		// Node Assassin.
		if (node > NODECOUNT)
		{
			// Too high a value!
			// Make my NODECOUNT an ASCII value so that I can print
			// it by reversing the convertion to binary done
			// earlier. The following two lines will be converted
			// by the compiler, so there is no run-time penalty for
			// the math here
			// 
			// Move from the 'tens' posiition into the '1' position
			// and add '0' to get the ASCII value.
			nodeASCII[0]=(NODECOUNT/10)+'0';
			// The modulous returns my real "one" position.
			nodeASCII[1]=(NODECOUNT%10)+'0';
			// nodeASCII was <NUL> terminated earlier at 3, so no
			// need to do it again here
			
			printMessage("ERROR: Max node value: ["); printMessage(nodeASCII); printMessage("]\n");
			printMessage("EOM\n");
			return;
		}
		
		// Check that the requested state is sane.
		if (state > 3)
		{
			// Node state can't be higher than '3' on this model.
			printMessage("ERROR: Invalid state.\n");
			printMessage("EOM\n");
			return;
		}
		
		// Check if this is an info request.
		if (0 == node)
		{
			// If the message request is '0', return states.
			// If the message request is '1', return NA info.
			if (0 == state)
			{
				// Send states
				printMessage("Node states: \n");
				
				// Make my NODECOUNT an ASCII value so that I
				// can print it by reversing the convertion to
				// binary done earlier.
				nodeASCII[0]=(NODECOUNT/10)+'0';
				nodeASCII[1]=(NODECOUNT%10)+'0';
				
				printMessage("- Node Count: "); printMessage(nodeASCII); printMessage("\n");
				
				/*
				NOTE: - Future optimization:
				The division and modulus in the loop can be
				expensive processing wise, as the compiler
				cannot do the calculation at compile time. As
				we are simply itteratively looping and
				incrementing, we can increment the ASCII value
				directly, removing the need for any division or
				modulus operations.
				*/
				
				// Loop through the supported number of nodes
				// and return their fence and feed states.
				for (int node=1; node<=NODECOUNT; node++)
				{
					// 'node' is the current, one-based
					// node number.
					nodeASCII[0]=(node/10)+'0';
					// The modulous returns my real one
					// position.
					nodeASCII[1]=(node%10)+'0';
					
					// Make this a bit more readable.
					node_power_pin=(((node*2)-1)+(FIRSTOUTPIN-1));
					node_reset_pin=((node*2)+(FIRSTOUTPIN-1));
					node_feed_pin=(node+(FIRSTINPIN-1));
					
					// Read in the current states.
					np_state = digitalRead(node_power_pin);
					nr_state = digitalRead(node_reset_pin);
					nf_state = digitalRead(node_feed_pin);
					
					// And finally report the states.
					printMessage("- Node "); printMessage(nodeASCII); printMessage(": ");
					printMessage("P"); printMessage((LOW == np_state) ? "0, " : "1, ");
					printMessage("R"); printMessage((LOW == nr_state) ? "0, " : "1, ");
					printMessage("F"); printMessage((LOW == nf_state) ? "0\n" : "1\n");
					
					// This is extra debug info for the
					// serial console.
					Serial.print(" P.Pin: "); Serial.println(node_power_pin);
					Serial.print(" R.Pin: "); Serial.println(node_reset_pin);
					Serial.print(" F.Pin: "); Serial.println(node_feed_pin);
				}
				printMessage("EOM\n");
			}
			else if (1 == state)
			{
				/* Setup some strings. */
				// MAC address.
				printMessage("Node info: \n");
				char macASCII[18]; // Enough room for 6 bytes
						   // of hex [12 digits], colon
						   // seperators (:) and the
						   // NULL terminator
				// IP Address, netmask and default gateway in
				// dotted decimal formats.
				char ipASCII[16];
				char nmASCII[16];
				char dgASCII[16];
				int j=0;
				
				// Generate the MAC address ASCII string.
				for(int i=0; i < (sizeof(mac) / sizeof(mac[0])); i++)
				{
					// If I have a value, that is, is '1'
					// or higher, start by inserting a 
					// colon (:) to seperate the octets.
					// This method avoids a preceeding ':'.
					if (i)
					{
						macASCII[j++] = ':';
					}
					// We're zero-padding single hex
					// values, so if this value is less
					// than 16 (0000 1111), add a leading
					// '0'.
					if (mac[i]<16)
					{
						macASCII[j] = '0';
						itoa(mac[i], &macASCII[(j)+1], 16);
					}
					else
					{
						itoa(mac[i], &macASCII[j], 16);
					}
					j+=2;
				}
				
				// Now we will generate the IP address, netmask
				// and default gateway ASCII strings.
				j=0;
				for (int i=0; i < (sizeof(ip) / sizeof(ip[0])); i++)
				{
					// If I have a value, that is, is '1'
					// or higher, start by inserting a 
					// period (.) to seperate the octets.
					if (i)
					{
						ipASCII[j++] = '.';
					}
					
					// Convert the integer to an ASCII.
					itoa(ip[i], &ipASCII[j++], 10);
					
					// Increment 'j' one or two places,
					// depending on the value of 'j'.
					if(ip[i]>9) j++;
					if(ip[i]>99) j++;
				}
				j=0;
				for (int i=0; i < (sizeof(nm) / sizeof(nm[0])); i++)
				{
					if (i)
					{
						nmASCII[j++] = '.';
					}
					itoa(nm[i], &nmASCII[j++], 10);
					if(nm[i]>9) j++;
					if(nm[i]>99) j++;
				}
				j=0;
				for (int i=0; i < (sizeof(ip) / sizeof(ip[0])); i++)
				{
					if (i)
					{
						dgASCII[j++] = '.';
					}
					itoa(dg[i], &dgASCII[j++], 10);
					if(dg[i]>9) j++;
					if(dg[i]>99) j++;
				}
				
				// Make my NODECOUNT an ASCII value so that I
				// can print it by reversing the convertion to
				// binary done earlier.
				nodeASCII[0]=(NODECOUNT/10)+'0';
				nodeASCII[1]=(NODECOUNT%10)+'0';
				
				// Print the info.
				printMessage("- Node Name: ..... "); printMessage(nodeName); printMessage("\n");
				printMessage("- Port Count: .... "); printMessage(nodeASCII); printMessage("\n");
				printMessage("- NAOS Version: .. "); printMessage(osVersion); printMessage("\n");
				printMessage("- Serial Number: . "); printMessage(serialNumber); printMessage("\n");
				printMessage("- Build Date: .... "); printMessage(buildDate); printMessage("\n");
				printMessage("- MAC address: ... "); printMessage(macASCII); printMessage("\n");
				printMessage("- IP address: .... "); printMessage(ipASCII); printMessage("\n");
				printMessage("- Subnet Mask: ... "); printMessage(nmASCII); printMessage("\n");
				printMessage("- Default Gateway: "); printMessage(dgASCII); printMessage("\n");
				printMessage("EOM\n");
			}
			else
			{
				// Unrecognized message request.
				printMessage("ERROR: Unknown message request.\n");
				printMessage("EOM\n");
			}
			
			return;
		}
		
		// If I am still alive, I am going to set a node to a given
		// state.
		
		// Subtract 1 from node to make it zero-based.
		node--;
		
		// Make the node number printable.
		nodeASCII[0]=((node+1)/10)+'0';
		nodeASCII[1]=((node+1)%10)+'0';
		
		// Which state I received will determine what I actually do to
		// the power and reset output pins.
		if (0 == state)
		{
			// Tell the user what is going to happen.
			printMessage("Releasing "); printMessage(nodeASCII); printMessage("\n");
			
			// Get prior states to make my return string a little
			// more useful.
			np_state = digitalRead(node_power_pin);
			nr_state = digitalRead(node_reset_pin);
			
			// Release power.
			digitalWrite(node_power_pin, LOW);
			printMessage(" - Power "); printMessage((LOW == np_state) ? "wasn't fenced.\n" : "released.\n");
			
			// Release reset.
			digitalWrite(node_reset_pin, LOW);
			printMessage(" - Reset "); printMessage((LOW == nr_state) ? "wasn't fenced.\n" : "released.\n");
			
			// Wait one second and then check that the pin states
			// are actually LOW. I could probably get away with a
			// smaller delay, but this works.
			delay(1000);
			
			// Check the current/new states
			np_state = digitalRead(node_power_pin);
			nr_state = digitalRead(node_reset_pin);
			
			// Report an error if either are still high. Not sure
			// how this might happen, but hey, let's be thorough.
			printMessage(" - Status: "); printMessage(((HIGH == np_state) || (HIGH == nr_state)) ? "ERROR! Fence failed to release.\n" : "SUCCESS!\n");
			printMessage("EOM\n");
		}
		else if (1 == state)
		{
			// Fence the node! This is perhaps the most critical
			// operation to get right. Start by telling the user
			// what we're going to do.
			printMessage("Fencing node "); printMessage(nodeASCII); printMessage(":\n");
			
			// Get prior states.
			np_state = digitalRead(node_power_pin);
			nr_state = digitalRead(node_reset_pin);
			
			// If either power or reset where HIGH already, release
			// them and wait one second. This will allow us to
			// re-run the fence attempt were an earlier one may
			// have failed.
			if (HIGH == np_state)
			{
				printMessage(" - Power was fenced, releasing.");
				digitalWrite(node_power_pin, LOW);
			}
			if (HIGH == nr_state)
			{
				printMessage(" - Reset was fenced, releasing.");
				digitalWrite(node_reset_pin, LOW);
			}
			
			// If either were HIGH, sleep for one second.
			if ((HIGH == np_state) || (HIGH == nr_state))
			{
				delay(1000);
			}
			
			// Fence the reset for one second to immediately
			// disable the node.
			digitalWrite(node_reset_pin, HIGH);
			printMessage(" - Reset fenced.\n");
			delay(1000);
			
			// Release reset so that we can hit the power next.
			// This is required because some machines will not
			// power down if the reset switch is closed.
			digitalWrite(node_reset_pin, LOW);
			printMessage(" - Reset released.\n");
			delay(1000);
			
			// Now fence the power button to begin the forced power
			// down. Then wait five seconds and check the power
			// feed state. 
			digitalWrite(node_power_pin, HIGH);
			printMessage(" - Power fenced.\n");
			delay(5000);
			int fence_ok=1;
			nf_state = digitalRead(node_feed_pin);
			
			// If the feed is still HIGH, wait another 25 seconds
			// and check a second time.
			if (HIGH == nf_state)
			{
				printMessage(" - WARNING: Node still on, waiting.\n");
				delay(25000);
				nf_state = digitalRead(node_feed_pin);
				
				// If it is still HIGH, error out.
				if (HIGH == nf_state)
				{
					printMessage(" - ERROR! Node still on. FENCE FAILED!\n");
					fence_ok=0;
				}
			}
			
			// Proceed if fence succeeded.
			if (1 == fence_ok)
			{
				printMessage(" - SUCCESS!\n");
				
				// Re-fence the reset switch to disable the
				// node's front-panel switches.
				digitalWrite(node_reset_pin, HIGH);
				printMessage(" - Node's front-panel switches locked.\n");
			}
			printMessage("EOM\n");
		}
		else if (2 == state)
		{
			// Hit the power switch for one second.
			// First check the current state so that I can properly
			// report what is happening.
			nf_state = digitalRead(node_feed_pin);
			if (HIGH == nf_state)
			{
				// The node is on, so report that we are
				// shutting down.
				printMessage("Initiating ACPI power down\n");
			}
			else
			{
				// The node was off, so report that we are
				// booting.
				printMessage("Booting node\n");
			}
			
			// Get prior states. If either are HIGH, Error out and
			// do nothing. The node needs to be released from the
			// fence before state 2 can be applied to it.
			np_state = digitalRead(node_power_pin);
			nr_state = digitalRead(node_reset_pin);
			if ((HIGH == np_state) || (HIGH == nr_state))
			{
				printMessage(" - ERROR! Node is fenced. Release and try again.\n");
			}
			else
			{
				// We're good to proceed.
				digitalWrite(node_power_pin, HIGH);
				printMessage(" - Power button closed.\n");
				delay(1000);
				digitalWrite(node_power_pin, LOW);
				printMessage(" - Power button opened.\n");
			}
			printMessage("EOM\n");
		}
		else if (3 == state)
		{
			// Hit the power switch for five seconds. Make sure the
			// power feed is low, and if not, wait another 25
			// seconds and check again.
			printMessage("Forcing power down of node "); printMessage(nodeASCII); printMessage(":\n");
			
			// If the node is off, then there is nothing to do.
			nf_state = digitalRead(node_feed_pin);
			if (LOW == nf_state)
			{
				// Node is off, so no need to proceed.
				printMessage(" - WARNING! Node is already off.\n");
			}
			else
			{
				// Fence power
				digitalWrite(node_power_pin, HIGH);
				printMessage(" - Forcing node off.\n");
				delay(5000);
				
				// Check that the power is off and wait another
				// 25 seconds if it isn't.
				int fence_ok=1;
				nf_state = digitalRead(node_feed_pin);
				if (HIGH == nf_state)
				{
					printMessage(" - WARNING! Node still on, waiting.\n");
					delay(25000);
					nf_state = digitalRead(node_feed_pin);
					if (HIGH == nf_state)
					{
						printMessage(" - ERROR! Node still on. FORCED SHUTDOWN FAILED!\n");
						fence_ok=0;
					}
				}
				
				// Proceed if fence succeeded.
				if (1 == fence_ok)
				{
					printMessage(" - SUCCESS!\n");
					digitalWrite(node_power_pin, LOW);
					printMessage(" - Fence released.\n");
				}
			}
			printMessage("EOM\n"); 
		}
	}
}

// The error handling function.
void printError(const char *message)
{
	// Print the message to the serial bus and the client. I know this is
	// dirty but it represents the one line string.
	printMessage("ERROR: Bad command: [" ); printMessage(message); printMessage("]\n" );
	printMessage("EOM\n");
}

void printMessage(const char *message)
{
	// Print the message to the serial bus and the client.
	Serial.print(message);
	server.write(message);
}
</source>

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