/*-
    * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
    * SNMP Java Client
    * ჻჻჻჻჻჻
    * Copyright 2023 MetricsHub
    * ჻჻჻჻჻჻
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as
    * published by the Free Software Foundation, either version 3 of the
   * License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  package org.metricshub.snmp.client;
  
  import uk.co.westhawk.snmp.pdu.BlockPdu;
  import uk.co.westhawk.snmp.stack.AsnObject;
  import uk.co.westhawk.snmp.stack.AsnObjectId;
  import uk.co.westhawk.snmp.stack.AsnOctets;
  import uk.co.westhawk.snmp.stack.PduException;
  import uk.co.westhawk.snmp.stack.SnmpConstants;
  import uk.co.westhawk.snmp.stack.SnmpContext;
  import uk.co.westhawk.snmp.stack.SnmpContextv2c;
  import uk.co.westhawk.snmp.stack.SnmpContextv3;
  import uk.co.westhawk.snmp.stack.SnmpContextv3Face;
  import uk.co.westhawk.snmp.stack.varbind;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  public class SnmpClient {
  
  	// Default SNMP port number
  	public static final int SNMP_PORT = 161;
  
  	// SNMP v1, v2c, v3
  	public static final int SNMP_V1 = 1;
  	public static final int SNMP_V2C = 2;
  	public static final int SNMP_V3 = 3;
  	public static final String SNMP_AUTH_MD5 = "MD5";
  	public static final String SNMP_AUTH_SHA = "SHA";
  	public static final String SNMP_AUTH_SHA256 = "SHA256";
  	public static final String SNMP_AUTH_SHA512 = "SHA512";
  	public static final String SNMP_AUTH_SHA224 = "SHA224";
  	public static final String SNMP_AUTH_SHA384 = "SHA384";
  	public static final String SNMP_PRIVACY_DES = "DES";
  	public static final String SNMP_PRIVACY_AES = "AES";
  	public static final String SNMP_PRIVACY_AES192 = "AES192";
  	public static final String SNMP_PRIVACY_AES256 = "AES256";
  	public static final String SNMP_NONE = "None";
  
      public static final Set<String> SNMP_PRIVACY_PROTOCOLS = Collections.unmodifiableSet( new HashSet<>(
      		Arrays.asList(SNMP_PRIVACY_DES, SNMP_PRIVACY_AES, SNMP_PRIVACY_AES192, SNMP_PRIVACY_AES256)));
      
      public static final Set<String> SNMP_AUTH_PROTOCOLS = Collections.unmodifiableSet( new HashSet<>(
      		Arrays.asList(SNMP_AUTH_MD5, SNMP_AUTH_SHA, SNMP_AUTH_SHA256, SNMP_AUTH_SHA512, SNMP_AUTH_SHA224, SNMP_AUTH_SHA384)));
      
  	private SnmpContext contextv1 = null;
  	private SnmpContextv2c contextv2c = null;
  	private SnmpContextv3 contextv3 = null;
  	private BlockPdu pdu;
  	private String host;
  	private int port;
  	private String community;
  	private int snmpVersion;
  	private String authUsername;
  	private String authType;
  	private String authPassword;
  	private String privacyType;
  	private String privacyPassword;
  	private int[] retryIntervals;
  	private String contextName;
  	private byte[] contextEngineID;
  	public static final String SOCKET_TYPE = "Standard";
  
  	/**
  	 * Creates an SNMPClient instance, which connects to the specified SNMP agent
  	 * with the specified credentials
  	 * (depending on the version of SNMP)
  	 * 
  	 * @param host            The hostname/IP address of the SNMP agent we're
  	 *                        querying
  	 * @param port            The port of the SNMP agent (should be 161)
  	 * @param version         The version of SNMP to use (1, 2 or 3)
  	 * @param retryIntervals  Timeout in milliseconds after which the elementary
  	 *                        operations will be retried
 	 * @param community       <i>(SNMP v1 and v2 only)</i> The SNMP community
 	 * @param authType        <i>(SNMP v3 only)</i> The authentication method:
 	 *                        "MD5", "SHA" or ""
 	 * @param authUsername    <i>(SNMP v3 only)</i> The username
 	 * @param authPassword    <i>(SNMP v3 only)</i> The password (in clear)
 	 * @param privacyType     <i>(SNMP v3 only)</i> The encryption type: "DES",
 	 *                        "AES" or ""
 	 * @param privacyPassword <i>(SNMP v3 only)</i> The encryption password
 	 * @param contextName     <i>(SNMP v3 only)</i> The context name
 	 * @param contextID       <i>(SNMP v3 only)</i> The context ID (??)
 	 * @throws IllegalArgumentException when specified authType, privType are
 	 *                                  invalid
 	 * @throws IllegalStateException    when the specified properties lead to
 	 *                                  something that cannot work (i.e. privacy
 	 *                                  without authentication)
 	 * @throws IOException              when cannot initialize the SNMP context
 	 */
 	public SnmpClient(String host, int port, int version, int[] retryIntervals,
 			String community,
 			String authType, String authUsername, String authPassword,
 			String privacyType, String privacyPassword,
 			String contextName, byte[] contextID) throws IOException {
 		// First, validate the inputs
 		validate(version, authType, privacyType);
 
 		// Sets the attributes of the class instance
 		this.host = host;
 		this.port = port;
 		this.snmpVersion = version;
 		this.retryIntervals = retryIntervals;
 		this.community = community;
 		this.authType = authType;
 		this.authUsername = authUsername;
 		this.authPassword = authPassword;
 		this.privacyType = privacyType;
 		this.privacyPassword = privacyPassword;
 		this.contextName = contextName;
 		this.contextEngineID = contextID;
 
 		// Properly create the SNMP context, based on these properties
 		initialize();
 	}
 
 	/**
 	 * Validate the specified inputs. Throws an IllegalArgumentException if needed.
 	 * 
 	 * @param version     Specified version of the SNMP protocol
 	 * @param authType    Specified authType
 	 * @param privacyType Specified privacyType
 	 * @throws IllegalArgumentException when invalid inputs are specified
 	 */
 	private void validate(int version, String authType, String privacyType) {
 
 		// In case of SNMP v3, check the authType and privType (if not empty)
 		if (version == SNMP_V3) {
 			if (authType != null) {
 				if (!authType.isEmpty()) {
 					if (! SNMP_AUTH_PROTOCOLS.contains(authType)) {
 						throw new IllegalArgumentException("Invalid authentication method '" + authType + "'." +
 								" (Valid options are: '" + SNMP_AUTH_MD5
 								+ "', '" + SNMP_AUTH_SHA
 								+ "', '" + SNMP_AUTH_SHA256
 								+ "', '" + SNMP_AUTH_SHA512
 								+ "', '" + SNMP_AUTH_SHA224
 								+ "', '" + SNMP_AUTH_SHA384
 								+ "', or empty)");
 					}
 				}
 			}
 
 			if (privacyType != null) {
 				if (!privacyType.isEmpty()) {
 					if (! SNMP_PRIVACY_PROTOCOLS.contains(privacyType)) {
 						throw new IllegalArgumentException(
 								"Invalid privacy method '" + privacyType + "'." + " (Valid options are:'" + SNMP_PRIVACY_DES
 								+ "', '" + SNMP_PRIVACY_AES + "', '" + SNMP_PRIVACY_AES192 + "', '" + SNMP_PRIVACY_AES256  + "', or empty)");
 					}
 				}
 			}
 		}
 	}
 
 	/**
 	 * Initialize the SNMPClient
 	 * <p>
 	 * Creates the context to connect to the SNMP agent. Required before any actual
 	 * operation is performed.
 	 * 
 	 * @throws IOException           when cannot create the SNMP context
 	 * @throws IllegalStateException when there is an inconsistency in the
 	 *                               properties that prevent us from moving forward
 	 */
 	private void initialize() throws IOException {
 
 		// SNMP v2c
 		if (snmpVersion == SNMP_V2C) {
 			contextv2c = new SnmpContextv2c(host, port, null, SOCKET_TYPE);
 			contextv2c.setCommunity(community);
 		}
 
 		// SNMP v3
 		else if (snmpVersion == SNMP_V3) {
 			int authProtocolCode = 0;
 			int privacyProtocolCode = 0;
 			boolean authenticate = false;
 			boolean privacy = false;
 
 			// Some sanity check with the "context"
 			if (contextEngineID == null) {
 				contextEngineID = new byte[0];
 			}
 			if (contextName == null) {
 				contextName = "";
 			}
 
 			// Verify the username
 			if (authUsername == null) {
 				authUsername = "";
 			}
 
 			// Verify and translate the authentication type
 			if (authType == null || authUsername == null || authPassword == null) {
 				authenticate = false;
 				authProtocolCode = SnmpContextv3Face.NO_AUTH_PROTOCOL;
 				authPassword = "";
 			} else if (authType.isEmpty() || authUsername.isEmpty() || authPassword.isEmpty()) {
 				authenticate = false;
 				authProtocolCode = SnmpContextv3Face.NO_AUTH_PROTOCOL;
 				authPassword = "";
 			} else if (authType.equals(SNMP_AUTH_MD5)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.MD5_PROTOCOL;
 			} else if (authType.equals(SNMP_AUTH_SHA)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.SHA1_PROTOCOL;
 			} else if (authType.equals(SNMP_AUTH_SHA256)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.SHA256_PROTOCOL;
 			} else if (authType.equals(SNMP_AUTH_SHA512)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.SHA512_PROTOCOL;
 			} else if (authType.equals(SNMP_AUTH_SHA224)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.SHA224_PROTOCOL;
 
 			} else if (authType.equals(SNMP_AUTH_SHA384)) {
 				authenticate = true;
 				authProtocolCode = SnmpContextv3Face.SHA384_PROTOCOL;
 			}
 
 			// Verify the privacy thing
 			if (privacyType == null || privacyPassword == null) {
 				privacy = false;
 			} else if (privacyType.isEmpty() || privacyPassword.isEmpty()) {
 				privacy = false;
 			} else if (privacyType.equals(SNMP_PRIVACY_DES)) {
 				privacy = true;
 				privacyProtocolCode = SnmpContextv3Face.DES_ENCRYPT;
 			} else if (privacyType.equals(SNMP_PRIVACY_AES)) {
 				privacy = true;
 				privacyProtocolCode = SnmpContextv3Face.AES_ENCRYPT;
 			} else if (privacyType.equals(SNMP_PRIVACY_AES192)) {
 			    privacy = true;
 			    privacyProtocolCode = SnmpContextv3Face.AES192_ENCRYPT;
 			} else if (privacyType.equals(SNMP_PRIVACY_AES256)) {
 			    privacy = true;
 			    privacyProtocolCode = SnmpContextv3Face.AES256_ENCRYPT;
 			}
 			// Privacy with no authentication is impossible
 			if (privacy && !authenticate) {
 				throw new IllegalStateException("Authentication is required for privacy to be enforced");
 			}
 
 			// Create the context
 			contextv3 = new SnmpContextv3(host, port, SOCKET_TYPE);
 			contextv3.setContextEngineId(contextEngineID);
 			contextv3.setContextName(contextName);
 			contextv3.setUserName(authUsername);
 			contextv3.setUseAuthentication(authenticate);
 			if (authenticate) {
 				contextv3.setUserAuthenticationPassword(authPassword);
 				contextv3.setAuthenticationProtocol(authProtocolCode);
 				contextv3.setUsePrivacy(privacy);
 				if (privacy) {
 					contextv3.setPrivacyProtocol(privacyProtocolCode);
 					contextv3.setUserPrivacyPassword(privacyPassword);
 				}
 			}
 		}
 
 		// SNMP v1 (default)
 		else {
 			contextv1 = new SnmpContext(host, port, SOCKET_TYPE);
 			contextv1.setCommunity(community);
 		}
 
 		// Small thing: set the prefix for hex values (default is "0x" but we're setting
 		// it to empty)
 		AsnOctets.setHexPrefix("");
 
 		// AsnObject.setDebug(15);
 
 	}
 
 	/**
 	 * Releases the resources associated to this instance
 	 * (or so at least we believe...)
 	 */
 	public void freeResources() {
 		if (contextv1 != null) {
 			contextv1.destroy();
 			contextv1 = null;
 		}
 		if (contextv2c != null) {
 			contextv2c.destroy();
 			contextv2c = null;
 		}
 		if (contextv3 != null) {
 			contextv3.destroy();
 			contextv3 = null;
 		}
 
 		if (pdu != null) {
 			pdu = null;
 		}
 	}
 
 	/**
 	 * Create the PDU and sets the timeout
 	 * <p>
 	 * Note: This method has been created just to avoid duplicate code in the get,
 	 * getNext and walk functions
 	 */
 	private void createPdu() {
 		// Create the PDU based on the proper context
 		if (snmpVersion == SNMP_V2C) {
 			pdu = new BlockPdu(contextv2c);
 		} else if (snmpVersion == SNMP_V3) {
 			pdu = new BlockPdu(contextv3);
 		} else {
 			pdu = new BlockPdu(contextv1);
 		}
 
 		// Set the timeout
 		if (retryIntervals != null) {
 			pdu.setRetryIntervals(retryIntervals);
 		}
 	}
 
 	/**
 	 * Perform a GET operation on the specified OID
 	 * 
 	 * @param oid OID on which to perform a GET operation
 	 * @return Value of the specified OID
 	 * @throws Exception in case of any problem
 	 */
 	public String get(String oid) throws Exception {
 		createPdu();
 		pdu.setPduType(BlockPdu.GET);
 		pdu.addOid(oid);
 		return sendRequest().value;
 	}
 
 	/**
 	 * Perform a GET operation on the specified OID and return the details of the
 	 * result (including the type of the value)
 	 * 
 	 * @param oid OID on which to perform a GET operation
 	 * @return A string in the form of the OID, "string" and the value, separated by
 	 *         tabs (\t)
 	 * @throws Exception in case of any problem
 	 */
 	public String getWithDetails(String oid) throws Exception {
 		createPdu();
 		pdu.setPduType(BlockPdu.GET);
 		pdu.addOid(oid);
 		SnmpResult result = sendRequest();
 		return result.oid + "\t" + result.type + "\t" + result.value;
 	}
 
 	/**
 	 * Perform a GETNEXT operation on the specified OID
 	 * 
 	 * @param oid OID on which to perform a GETNEXT operation
 	 * @return A string in the form of the OID, "string" and the value, separated by
 	 *         tabs (\t)
 	 * @throws Exception in case of any problem
 	 */
 	public String getNext(String oid) throws Exception {
 		createPdu();
 		pdu.setPduType(BlockPdu.GETNEXT);
 		pdu.addOid(oid);
 		SnmpResult result = sendRequest();
 		return result.oid + "\t" + result.type + "\t" + result.value;
 	}
 
 	/**
 	 * Perform a WALK, i.e. a series of GETNEXT operations until we fall off the
 	 * tree
 	 * 
 	 * @param oid Root OID of the tree
 	 * @return Result of the WALK operation, as a long String. Each pair of
 	 *         oid/value is separated with a linefeed (at least, for now!)
 	 * @throws Exception
 	 * @throws IllegalArgumentException for bad specified OIDs
 	 */
 	public String walk(String oid) throws Exception {
 
 		StringBuilder walkResult = new StringBuilder();
 		String currentOID;
 		SnmpResult getNextResult;
 
 		// Sanity check?
 		if (oid == null) {
 			throw new IllegalArgumentException("Invalid SNMP Walk OID: null");
 		}
 		if (oid.length() < 3) {
 			throw new IllegalArgumentException("Invalid SNMP Walk OID: \"" + oid + "\"");
 		}
 
 		// Now, something special:
 		// In the walk loop below, we will catch any exception and break out of the loop
 		// if anything happens. At that point, we simply return what we have, i.e. just
 		// as if everything was okay. Doing so, we fail to report authentication
 		// problems.
 		// So, the code using this will think it's just okay, even though the QA team
 		// intentionally put bad credentials to verify the error message... See
 		// MATSYA-464.
 		//
 		// So, we're going to first run a getNext() for nothing, just so that
 		// this call will throw the proper exception in case of credentials problems.
 		getNext(oid);
 
 		currentOID = oid;
 		do {
 			createPdu();
 			pdu.setPduType(BlockPdu.GETNEXT);
 			pdu.addOid(currentOID);
 			try {
 				getNextResult = sendRequest();
 			} catch (Exception e) {
 				// Something wrong? Get out of the loop and return what we have
 				break;
 			}
 
 			currentOID = getNextResult.oid;
 			if (!currentOID.startsWith(oid)) {
 				// We're off the tree, so get out of the loop
 				break;
 			}
 
 			// Append the result
 			walkResult.append(currentOID + "\t" + getNextResult.type + "\t" + getNextResult.value + "\n");
 
 		} while (walkResult.length() < 10 * 1048576); // 10 MB is the limit for the result of our WALK operation. Should
 														// be enough.
 
 		// Remove the trailing \n (if any)
 		int resultLength = walkResult.length();
 		if (resultLength > 0) {
 			return walkResult.substring(0, resultLength - 1);
 		}
 
 		// If nothing, return an empty string
 		return "";
 	}
 
 	/**
 	 * Read the content of an SNMP table
 	 * 
 	 * @param rootOID           Root OID of the SNMP table
 	 * @param selectColumnArray Array of numbers specifying the column numbers of
 	 *                          the array to be read. Use "ID" for the row number.
 	 * @return A semicolon-separated list of values
 	 * @throws IllegalArgumentException when the specified arguments are wrong
 	 * @throws Exception                when the underlying SNMP API throws one
 	 */
 	public List<List<String>> table(String rootOID, String[] selectColumnArray) throws Exception {
 
 		// Sanity check
 		if (rootOID == null) {
 			throw new IllegalArgumentException("Invalid SNMP Table OID: null");
 		}
 		if (rootOID.length() < 3) {
 			throw new IllegalArgumentException("Invalid SNMP Table OID: \"" + rootOID + "\"");
 		}
 		if (selectColumnArray == null) {
 			throw new IllegalArgumentException("Invalid SNMP Table column numbers: null");
 		}
 		if (selectColumnArray.length < 1) {
 			throw new IllegalArgumentException("Invalid SNMP Table column numbers: none");
 		}
 
 		// First of all, retrieve the list of IDs in the table
 		// To do so, we need to see what is the first column number available (it may
 		// not be 1)
 		createPdu();
 		pdu.setPduType(BlockPdu.GETNEXT);
 		pdu.addOid(rootOID);
 		String firstValueOid = sendRequest().oid;
 		if (firstValueOid.isEmpty() || !firstValueOid.startsWith(rootOID)) {
 			// Empty table
 			return new ArrayList<>();
 		}
 
 		int tempIndex = firstValueOid.indexOf(".", rootOID.length() + 2);
 		if (tempIndex < 0) {
 			// Weird case, there is no "." after the rootOID in the OID of the first value
 			// we successfully got in the table
 			return new ArrayList<>();
 		}
 		String firstColumnOid = firstValueOid.substring(0, tempIndex);
 		int firstColumnOidLength = firstColumnOid.length();
 
 		// Now, find the list of row IDs in this column. We're going to do something
 		// like a walk, except we don't care about the values. Just the OIDs.
 		ArrayList<String> IDArray = new ArrayList<String>(0);
 		String currentOID = firstColumnOid;
 		SnmpResult getNextResult;
 		do {
 			// Get next until we get out of the tree
 			createPdu();
 			pdu.setPduType(BlockPdu.GETNEXT);
 			pdu.addOid(currentOID);
 			getNextResult = sendRequest();
 
 			currentOID = getNextResult.oid;
 
 			// Outside? Exit!
 			if (!currentOID.startsWith(firstColumnOid)) {
 				break;
 			}
 
 			// Add the right part of the OID in the list of IDs (the part to the right of
 			// the column OID)
 			IDArray.add(currentOID.substring(firstColumnOidLength + 1));
 
 		} while (IDArray.size() < 10000); // Not more than 10000 lines, please...
 
 		// And finally, build the result table
 		List<List<String>> tableResult = new ArrayList<>();
 		for (String ID : IDArray) {
 			// For each row...
 			List<String> row = new ArrayList<>();
 			for (String column : selectColumnArray) {
 				// For each column...
 
 				// If the column has to provide the ID of the row
 				if (column.equals("ID")) {
 					row.add(ID);
 				} else {
 					// Keep going, even in case of a failure
 					try {
 						row.add(get(rootOID + "." + column + "." + ID));
 					} catch (Exception e) {
 						row.add("");
 					}
 				}
 			}
 			tableResult.add(row);
 		}
 
 		// Return the result
 		return tableResult;
 	}
 
 	/**
 	 * Sends the SNMP request and perform some minor interpretation of the result
 	 * 
 	 * @return Result of the query in the form of a couple {oid;value} (SnmpResult)
 	 * @throws PduException when an error happens at the SNMP layer
 	 * @throws IOException  when an error occurs at the network layer
 	 * @throws Exception    when we cannot get the value of the specified OID,
 	 *                      because it does not exist
 	 *                      <p>
 	 *                      <li>In case of no such OID, an exception is thrown.
 	 *                      <li>In case of empty value, the result will have the oid
 	 *                      and an empty value.
 	 */
 	private SnmpResult sendRequest() throws PduException, IOException, Exception {
 
 		// Declarations
 		SnmpResult result = new SnmpResult();
 
 		// Send the SNMP request
 		varbind var = pdu.getResponseVariableBinding();
 
 		// Retrieve the OID and value of the response (a varbind)
 		AsnObjectId oid = var.getOid();
 		AsnObject value = var.getValue();
 
 		// No such OID? Throw an exception (this needs to be caught gracefully by other
 		// functions)
 		byte valueType = value.getRespType();
 		if (valueType == SnmpConstants.SNMP_VAR_NOSUCHOBJECT ||
 				valueType == SnmpConstants.SNMP_VAR_NOSUCHINSTANCE ||
 				valueType == SnmpConstants.SNMP_VAR_ENDOFMIBVIEW) {
 			throw new Exception(value.getRespTypeString());
 		}
 
 		// Empty?
 		else if (valueType == SnmpConstants.ASN_NULL) {
 			result.oid = oid.toString();
 			result.type = "null";
 		}
 
 		// ASN_OCTET_STRING? (special case, because it may need to be displayed as an
 		// hexadecimal string)
 		// Normally, the API should take care of that, but this is not the case for
 		// 0x00:00:00:00 values, which are displayed as empty values
 		else if (valueType == SnmpConstants.ASN_OCTET_STR) {
 
 			result.oid = oid.toString();
 			result.type = "ASN_OCTET_STR";
 
 			// Map the value to the specific AsnOctets sub-class
 			AsnOctets octetStringValue = (AsnOctets) value;
 
 			// First, convert the value as a string, using toString().
 			// AsnOctets.toString() will convert the value to a normal string (with ASCII
 			// chars)
 			// or to the hexadecimal version of it, like 0x00:30:31:32 when the "normal"
 			// string is
 			// not printable
 			String octetStringValuetoString = octetStringValue.toString();
 
 			// Then forcibly convert the value to its hexadecimal representation, but
 			// replace ':' with blank spaces, to match with what PATROL does
 			String octetStringValuetoHex = octetStringValue.toHex().replace(':', ' ');
 
 			// So, if the toString() and the toHex() value have the same length, it means
 			// that toString() is actually returning
 			// the hexadecimal representation (yeah, there is no other way to retrieve that,
 			// the SNMP API does not tell us
 			// whether the value is printable or not)
 			// If the SNMP API judges that the value is not printable, then we will use the
 			// toHex() value, with ':' replaced with blank spaces.
 			// But there is another case: if the original value is just a series of 0x00
 			// (nul) chars, the SNMP API converts that to an
 			// empty string, while we need to actually display 00 00 00 00...
 			// That's what we're doing in the code below
 
 			// If octetStringValuetoString is empty while the original value's length was
 			// greater than 0, then we'll need to convert it to hexadecimal
 			if (octetStringValuetoString.isEmpty() && octetStringValue.getBytes().length > 0) {
 				result.value = octetStringValuetoHex;
 			} else if (octetStringValuetoString.length() == octetStringValuetoHex.length()) {
 				result.value = octetStringValuetoHex;
 			} else {
 				result.value = octetStringValuetoString;
 			}
 		}
 
 		// Sets the result object
 		else {
 			result.oid = oid.toString();
 			result.type = value.getRespTypeString();
 			result.value = value.toString();
 		}
 
 		return result;
 
 	} // end of sendRequest
 
 }// end of class - SNMPClient