SNMPMgr Component

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The SNMPMgr component is used to implement UDP-based SNMP Management Applications.

Syntax

TipnSNMPMgr

Remarks

The SNMPMgr component implements a UDP-based standard SNMP Manager as specified in the SNMP RFCs. The component supports SNMP v1, v2c, and v3.

The component provides both encoding/decoding and transport capabilities, making the task of developing a custom SNMP manager as simple as setting a few key properties and handling a few events. SNMP data, such as for instance SNMP object id-s (OID-s) are exchanged as text strings, thus further simplifying the task of handling them.

The component is activated/deactivated by calling the Activate or Deactivate method. These methods enable or disable sending and receiving. The activation status can be found in the Active property.

Messages are received through events such as Response, Trap, or InformRequest. SNMP Traps are received through the Trap event.

Messages are sent to other agents or managers by using component's methods such as SendGetRequest, SendGetNextRequest, SendGetBulkRequest, SendSetRequest, and SendInformRequest.

SNMP OIDs, types, and values are provided in the Objects collection of SNMP objects for both sent and received packets.

SNMPv3 USM security is enabled by setting properties such as User, AuthenticationPassword, and EncryptionPassword and calling the Discover method to bind to a particular agent (RemoteEngineId). Upon successful discovery, received packets are checked for integrity (authentication) and timeliness. Note that the discovery step is optional, and may be avoided if the values for RemoteEngineId, RemoteEngineBoots, and RemoteEngineTime are known in advance and provided to the component through the respective properties.

By default, the component operates synchronously (except for the Discover method), sending a request and waiting until the corresponding response has been received. This behavior may be overridden by setting Timeout to 0, in which case the component returns control immediately after a send, and responses are received exclusively through the Response event.

Property List

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The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the component with short descriptions. Click on the links for further details.

AcceptData Property (SNMPMgr Component)

Enables or disables data reception.

Syntax

property AcceptData: Boolean read get_AcceptData write set_AcceptData;

Default Value

true

Remarks

Setting the property to False temporarily disables data reception. Setting the property to True re-enables data reception.

This property is not available at design time.

Active Property (SNMPMgr Component)

Indicates whether the component is active.

Syntax

property Active: Boolean read get_Active write set_Active;

Default Value

false

Remarks

This property indicates whether the component is currently active and can send or receive data.

The component will be automatically activated if it is not already and you attempt to perform an operation which requires the component to be active.

Note: Use the Activate or Deactivate method to control whether the component is active.

This property is not available at design time.

AuthenticationPassword Property (SNMPMgr Component)

The password used for SNMPv3 authentication.

Syntax

property AuthenticationPassword: String read get_AuthenticationPassword write set_AuthenticationPassword;

Default Value

''

Remarks

Every time EncryptionPassword, AuthenticationPassword, or RemoteEngineId are set, a localized key is computed automatically, and cached internally.

AuthenticationProtocol Property (SNMPMgr Component)

The authentication protocol used for SNMPv3 packets.

Syntax

property AuthenticationProtocol: TipnTSNMPAuthenticationAlgorithms read get_AuthenticationProtocol write set_AuthenticationProtocol;

TipnTSNMPAuthenticationAlgorithms = (
  authpHMACMD596,
  authpHMACSHA96,
  authpHMAC192SHA256,
  authpHMAC384SHA512
);

Default Value

authpHMACMD596

Remarks

This property defines the authentication protocol used when SNMPVersion is set to snmpverV3. Possible values are:

• 1 (HMAC-MD5-96 - default)
• 2 (HMAC-SHA-96)
• 3 (HMAC-192-SHA-256)
• 4 (HMAC-384-SHA-512)

This property is not available at design time.

Community Property (SNMPMgr Component)

The community string used to authenticate SNMP packets.

Syntax

property Community: String read get_Community write set_Community;

Default Value

'public'

Remarks

Must match the community name that is specified on the agent.

Typical values are "public" or "private".

This property is used for all SNMP packets sent by the component.

EncryptionAlgorithm Property (SNMPMgr Component)

The encryption algorithm used for SNMPv3 packets.

Syntax

property EncryptionAlgorithm: TipnTSNMPEncryptionAlgorithms read get_EncryptionAlgorithm write set_EncryptionAlgorithm;

TipnTSNMPEncryptionAlgorithms = (
  encraDES,
  encraAES,
  encra3DES,
  encraAES192,
  encraAES256
);

Default Value

encraDES

Remarks

In order to use encryption, you must set the EncryptionPassword property. The supported algorithms for encryption are:

This property is not available at design time.

EncryptionPassword Property (SNMPMgr Component)

The password used for SNMPv3 privacy.

Syntax

property EncryptionPassword: String read get_EncryptionPassword write set_EncryptionPassword;

Default Value

''

Remarks

Every time EncryptionPassword, AuthenticationPassword, or RemoteEngineId are set, a localized key is computed automatically, and cached internally.

ErrorDescription Property (SNMPMgr Component)

Description of the status code for the last SNMP packet received by the component.

Syntax

property ErrorDescription: String read get_ErrorDescription;

Default Value

'0'

Remarks

Please refer to the ErrorStatus property for more information.

This property is read-only and not available at design time.

ErrorIndex Property (SNMPMgr Component)

Index of the first variable (object) that caused an error from the last SNMP response.

Syntax

property ErrorIndex: Integer read get_ErrorIndex;

Default Value

0

Remarks

This property is used in conjunction with the ErrorStatus property, and refers to the object that caused the error reported in the last SNMP response. This value is parsed directly from the SNMP response, which will be a one-based value, so a value of i here maps to index i-1 in the Objects collection.

The ErrorIndex property has no meaning when the ErrorStatus property is 0 (no error).

This property is read-only and not available at design time.

ErrorStatus Property (SNMPMgr Component)

Status code for the last SNMP packet received by the component.

Syntax

property ErrorStatus: Integer read get_ErrorStatus;

Default Value

0

Remarks

This property is used in conjunction with the ErrorIndex property, which denotes the index of the variable in error. The ErrorDescription property provides a textual description of the error.

The following is a list of valid SNMP status code values:

The ErrorIndex parameter indicates the index of the first variable (object) that caused an error. The default value is 0.

Variable indexes start with 0. ErrorIndex has no meaning when ErrorStatus is 0 (no error).

The default value is 0 (no error).

This property is read-only and not available at design time.

LocalEngineId Property (SNMPMgr Component)

The Engine Id of the SNMP Manager.

Syntax

property LocalEngineId: String read get_LocalEngineId write set_LocalEngineId;
property LocalEngineIdB: TBytes read get_LocalEngineIdB write set_LocalEngineIdB;

Default Value

''

Remarks

This property is only used for SNMPv3 packets (when SNMPVersion is 3).

LocalHost Property (SNMPMgr Component)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

property LocalHost: String read get_LocalHost write set_LocalHost;

Default Value

''

Remarks

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multi-homed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

LocalPort Property (SNMPMgr Component)

The port in the local host where the SNMP Manager is bound to.

Syntax

property LocalPort: Integer read get_LocalPort write set_LocalPort;

Default Value

0

Remarks

The LocalPort property must be set before the component is activated (Active is set to True). It instructs the component to bind to a specific port (or communication endpoint) in the local machine. The default port is 0 (random port). If you would like to receive traps, set LocalPort to 162 (standard trap port). However, it is recommended that the SNMPTrapMgr component be used for listening to traps, because SNMPMgr is limited to receiving SNMPv3 traps from a single agent only. SNMPTrapMgr does not have this limitation.

LocalPort cannot be changed once the component is Active. Any attempt to set the LocalPort property when the component is Active will generate an error.

Note: on macOS and iOS, root permissions are required to set LocalPort to any value below 1024.

Objects Property (SNMPMgr Component)

The objects in the current request.

Syntax

property Objects: TipnSNMPObjectList read get_Objects write set_Objects;

Remarks

The SNMP objects being sent or received in the current request. The collection is first cleared, then populated every time an SNMP packet is received. It is also used to create outgoing SNMP packets.

Please refer to the SNMPObject type for a complete list of fields.

RemoteEngineBoots Property (SNMPMgr Component)

The remote engine boots (SNMPv3).

Syntax

property RemoteEngineBoots: Integer read get_RemoteEngineBoots write set_RemoteEngineBoots;

Default Value

0

Remarks

This property is used in conjunction with the RemoteEngineTime property. Please refer to the description of the RemoteEngineTime property, and the Discover method for further information.

RemoteEngineId Property (SNMPMgr Component)

The Engine Id of the remote agent.

Syntax

property RemoteEngineId: String read get_RemoteEngineId write set_RemoteEngineId;
property RemoteEngineIdB: TBytes read get_RemoteEngineIdB write set_RemoteEngineIdB;

Default Value

''

Remarks

This property is only used for SNMPv3 packets (see SNMPVersion), and is reset every time RemoteHost or RemotePort changes.

RemoteEngineId is normally discovered through the Discover method. However, by manually supplying a value for the property, RemoteEngineId discovery step may be eliminated, thus avoiding the extra roundtrip to the agent (RemoteEngineBoots and RemoteEngineTime are also required for User authentication - please refer to the Discover method for more information).

RemoteEngineTime Property (SNMPMgr Component)

The remote engine time (SNMPv3).

Syntax

property RemoteEngineTime: Integer read get_RemoteEngineTime write set_RemoteEngineTime;

Default Value

0

Remarks

RemoteEngineTime is used by SNMPv3 authentication to ensure timeliness of requests, and avoid replay attacks.

The value of RemoteEngineTime is provided as what is expected to be the current value of the remote engine clock based on a cached time differential between the remote engine clock and the local engine time obtained during the discovery process (see Discover).

This property is used in conjunction with RemoteEngineBoots. Please refer to the RemoteEngineBoots property and the Discover method for more information.

RemoteHost Property (SNMPMgr Component)

The address of the remote host. Domain names are resolved to IP addresses.

Syntax

property RemoteHost: String read get_RemoteHost write set_RemoteHost;

Default Value

''

Remarks

The RemoteHost property specifies the IP address (IP number in dotted internet format) or Domain Name of the host SNMP requests or traps are sent to.

If RemoteHost is set to 255.255.255.255, the component broadcasts data on the local subnet.

If the RemoteHost property is set to a Domain Name, a DNS request is initiated and upon successful termination of the request, the RemoteHost property is set to the corresponding address. If the search is not successful, an error is returned.

RemotePort Property (SNMPMgr Component)

The port where the remote SNMP agent is listening.

Syntax

property RemotePort: Integer read get_RemotePort write set_RemotePort;

Default Value

161

Remarks

The RemotePort is the port on the RemoteHost to send SNMP requests to.

A valid port number (a value between 1 and 65535) is required. The default value is 161.

RequestId Property (SNMPMgr Component)

The request-id to mark outgoing packets with.

Syntax

property RequestId: Integer read get_RequestId write set_RequestId;

Default Value

1

Remarks

If a custom value is needed for RequestId, the property must be set before sending the request. The component increments RequestId automatically after sending each packet.

This property is not available at design time.

SNMPVersion Property (SNMPMgr Component)

Version of SNMP used for outgoing requests.

Syntax

property SNMPVersion: TipnTSNMPVersions read get_SNMPVersion write set_SNMPVersion;

TipnTSNMPVersions = (
  snmpverV1,
  snmpverV2c,
  snmpverV3
);

Default Value

snmpverV2c

Remarks

This property takes one of the following values:

StoreWalkObjects Property (SNMPMgr Component)

Tells the component whether or not to store returned objects.

Syntax

property StoreWalkObjects: Boolean read get_StoreWalkObjects write set_StoreWalkObjects;

Default Value

true

Remarks

When a Walk is performed, this property tells the component whether or not to store the objects that are returned by the server in the Objects collection. If the data is accumulated through the events, and not desired to be saved by the component, set this property to false.

Timeout Property (SNMPMgr Component)

A timeout for the component.

Syntax

property Timeout: Integer read get_Timeout write set_Timeout;

Default Value

60

Remarks

If the Timeout property is set to 0, all operations return immediately, potentially failing with a WOULDBLOCK error if data cannot be sent immediately.

If Timeout is set to a positive value, data is sent in a blocking manner and the component will wait for the operation to complete before returning control. The component will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of Timeout seconds.

The component will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the component raises an exception.

Please note that by default, all timeouts are inactivity timeouts, i.e. the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 60 seconds.

User Property (SNMPMgr Component)

The user name used for SNMPv3 authentication.

Syntax

property User: String read get_User write set_User;

Default Value

''

Remarks

If authentication is desired, this property must be set before the component attempts to connect to an SNMPv3 Agent.

WalkLimit Property (SNMPMgr Component)

The limit of oid's returned in a walk.

Syntax

property WalkLimit: Integer read get_WalkLimit write set_WalkLimit;

Default Value

0

Remarks

This property specifies the limit of how many oid's are to be traversed during an SNMP Walk. If set to 0, the component will traverse all oid's in the specified table that are lexographically greater than the value of the specified table oid.

Activate Method (SNMPMgr Component)

Activates the component.

Syntax

procedure Activate();

Remarks

This method activates the component and will allow it to send or receive data.

The component will be automatically activated if it is not already and you attempt to perform an operation which requires the component to be active.

Note: Use the Active property to check whether the component is active.

Config Method (SNMPMgr Component)

Sets or retrieves a configuration setting.

Syntax

function Config(ConfigurationString: String): String;

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Deactivate Method (SNMPMgr Component)

Deactivates the component.

Syntax

procedure Deactivate();

Remarks

This method deactivates the component and will prohibit it from sending and receiving data.

Note: Use the Active property to check whether the component is active.

Discover Method (SNMPMgr Component)

Performs SNMPv3 discovery.

Syntax

procedure Discover();

Remarks

When the method is called an SNMPv3 engine discovery request is sent to RemoteHost.

If an AuthenticationPassword is provided, the engine id discovery request is followed by an engine time discovery request, as required by the SNMPv3 User Security Model (USM). In this case Timeout must be set to a non-zero value before calling Discover and the component will wait until a response is received from RemoteHost.

The DiscoveryResponse event is fired upon receipt of a valid discovery response and the values of RemoteEngineId, RemoteEngineBoots, and RemoteEngineTime will then be updated with the received Engine Id, Time, and Boots.

DoEvents Method (SNMPMgr Component)

Processes events from the internal message queue.

Syntax

procedure DoEvents();

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

HashPasswords Method (SNMPMgr Component)

Hashes all passwords in the cache.

Syntax

procedure HashPasswords();

Remarks

Forces computation of all passwords hashes in the cache. Used together with the HashPassword event to enable implementations of external password hash storage.

Interrupt Method (SNMPMgr Component)

Interrupt the current method.

Syntax

procedure Interrupt();

Remarks

If there is no method in progress, Interrupt simply returns, doing nothing.

Reset Method (SNMPMgr Component)

Clears the object arrays.

Syntax

procedure Reset();

Remarks

Clears the object arrays, and sets the trap and error properties to their default values. This is useful for reinitializing all the properties that are used to create outgoing packets before building a new packet.

Note: SNMPVersion will be reset to snmpverV2c (2).

SendGetBulkRequest Method (SNMPMgr Component)

Send a GetBulkRequest packet.

Syntax

procedure SendGetBulkRequest(NonRepeaters: Integer; MaxRepetitions: Integer);

Remarks

Sends a GetBulkRequest packet. This is only available for SNMP versions 2 and 3.

NonRepeaters specifies the number of variables for which a single lexicographic successor is to be returned.

MaxRepetitions specifies the number of lexicographic successors to be returned for variables other than those in the NonRepeaters list.

The object identifiers, types, and values for the request are taken from the Objects collection.

A GetBulkRequest is very similar to a GetNextRequest, the difference is that Getbulk performs a continuous GetNext operation based on the MaxRepitions value. The NonRepeaters value will determine the number of Objects for which a simple GetNext operation should be performed. For the remaining variables, a continuous GetNext operation is performed based on the MaxRepitions value.

So if you send a request containing X objects, the agent will perform N simple GetNext operations and M continuous GetNext operations X - N times. With X being the number of objects received, N being the number of NonRepeaters, and M being the number of MaxRepitions. Thus the SNMPMgr is expecting to receive N + M x (X - N) objects, assuming that each object has M successors.

Example (Sending a GetBulk Request)

SNMPControl.RemoteHost = "MyAgent" SNMPControl.ObjCount = 2 SNMPControl.ObjId(0) = "1.3.6.1.2.1.1.1.0" SNMPControl.objId(1) = "1.3.6.1.2.1.1.3.0" SNMPControl.SendGetBulkRequest(1,4)

The code sample above will send a GetBulkRequest with 1 non repeater, and a maxrepetitions of 4. Since there is only 1 non repeater, only one ObjID will "not repeat" and will only return one successor. The rest of the ObjID's (in this case, only 1) will return 4 successors. This particular example will return the following ObjID's:

SendGetNextRequest Method (SNMPMgr Component)

Send GetNextRequest packet.

Syntax

procedure SendGetNextRequest();

Remarks

Sends a GetNextRequest packet. The object identifiers, types, and values for the request are taken from the Objects collection.

Example (Sending a GetNext Request)

SNMPControl.ObjCount = 2 SNMPControl.ObjId(0) = "1.3.6.1.2.1.1.1.0" SNMPControl.SendGetNextRequest() The agent will respond with the "next" (relative to the ObjID(s) you specify) OID in the table.

SendGetRequest Method (SNMPMgr Component)

Send GetRequest packet.

Syntax

procedure SendGetRequest();

Remarks

Sends a GetRequest packet. The object identifiers, types, and values for the request are taken from the Objects collection.

Example (Sending a GetRequest)

SNMPControl.RemoteHost = "MyAgent" SNMPControl.ObjCount = 2 SNMPControl.ObjId(0) = "1.3.6.1.2.1.1.1.0" SNMPControl.ObjId(1) = "1.3.6.1.2.1.1.2.0" SNMPControl.SendGetRequest()

SendInformRequest Method (SNMPMgr Component)

Send an InformRequest packet.

Syntax

procedure SendInformRequest();

Remarks

Sends an InformRequest packet. The object identifiers, types, and values for the request are taken from the Objects collection.

SendSetRequest Method (SNMPMgr Component)

Send Set Request packet.

Syntax

procedure SendSetRequest();

Remarks

Sends a SetRequest packet. The object identifiers, types, and values for the request are taken from the Objects collection.

Example (Sending a SetRequest)

SNMPControl.RemoteHost = "MyAgent" SNMPControl.ObjCount = 1 SNMPControl.ObjId(0) = "1.3.6.1.2.1.1.1.0" SNMPControl.ObjValue(0) = "New Value" SNMPControl.ObjType(0) = otOctetString SNMPControl.SendSetRequest()

Value Method (SNMPMgr Component)

Returns the value corresponding to an OID.

Syntax

function Value(OID: String): String;

Remarks

If the OID does not exist in the Objects collection, a trappable error is generated.

Please refer to the SNMPObject type for more information.

Walk Method (SNMPMgr Component)

Does an SNMP walk starting with the specified oid.

Syntax

procedure Walk(TableOid: String);

Remarks

A walk will traverse all OIDs in the TableOid that are lexographically greater than the value of the TableOid.

The results of the walk may be obtained through the Response events. During the event, the current returned object will exist inside of the Objects collection. If StoreWalkObjects is set to true, the Objects collection will contain all returned objects when the Walk completes.

Use the WalkLimit property to regulate how many objects the walk will traverse in the table.

NOTE: The collection of objects is cleared before the walk begins.

BadPacket Event (SNMPMgr Component)

Fired for erroneous and/or malformed messages.

Syntax

type TBadPacketEvent = procedure (
  Sender: TObject;
  Packet: String;
  PacketB: TBytes;
  const SourceAddress: String;
  SourcePort: Integer;
  ErrorCode: Integer;
  const ErrorDescription: String;
  var Report: Boolean
) of Object;

property OnBadPacket: TBadPacketEvent read FOnBadPacket write FOnBadPacket;

Remarks

The full message is provided in the Packet parameter.

The BadPacket event is also fired when authentication fails for received packets due to a bad password or other reasons.

If the Report parameter is set to True, an unauthenticated error report will be sent to the client, otherwise the packet will be silently ignored.

DiscoveryRequest Event (SNMPMgr Component)

Fired when an SNMPv3 discovery packet is received.

Syntax

type TDiscoveryRequestEvent = procedure (
  Sender: TObject;
  EngineId: String;
  EngineIdB: TBytes;
  EngineBoots: Integer;
  EngineTime: Integer;
  const User: String;
  SecurityLevel: Integer;
  const SourceAddress: String;
  SourcePort: Integer;
  var Respond: Boolean
) of Object;

property OnDiscoveryRequest: TDiscoveryRequestEvent read FOnDiscoveryRequest write FOnDiscoveryRequest;

Remarks

EngineId, EngineBoots, EngineTime, and User are the values received from SourceAddress.

For SNMPv3, the User parameter shows the user that was supplied with the packet. This parameter MUST be used together with the SecurityLevel parameter which shows the level of security in the message.

The SecurityLevel parameter shows whether the request has been authenticated. If SecurityLevel is 0, the request has NOT been authenticated (i.e. the packet signature has not been verified). For an authenticated, non encrypted request, SecurityLevel is 1. For an authenticated and encrypted request, SecurityLevel is 2.

Respond is True by default, and will automatically send a response using the value in LocalEngineId. To suppress the response, set Respond to False.

The value returned to SourceAddress for EngineBoots is always 0, and EngineTime is the number of seconds since January 1st, 1970 (GMT).

DiscoveryResponse Event (SNMPMgr Component)

Fired when an SNMPv3 discovery response is received.

Syntax

type TDiscoveryResponseEvent = procedure (
  Sender: TObject;
  EngineId: String;
  EngineIdB: TBytes;
  EngineBoots: Integer;
  EngineTime: Integer;
  const User: String;
  SecurityLevel: Integer;
  const SourceAddress: String;
  SourcePort: Integer
) of Object;

property OnDiscoveryResponse: TDiscoveryResponseEvent read FOnDiscoveryResponse write FOnDiscoveryResponse;

Remarks

EngineId, EngineBoots, EngineTime, and User are the values received from SourceAddress and SourcePort.

The SecurityLevel parameter shows whether the request has been authenticated. If SecurityLevel is 0, the request has NOT been authenticated (i.e. the packet signature has not been verified). For an authenticated request, SecurityLevel is at least 1.

Error Event (SNMPMgr Component)

Fired when information is available about errors during data delivery.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ErrorCode: Integer;
  const Description: String
) of Object;

property OnError: TErrorEvent read FOnError write FOnError;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component raises an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

HashPassword Event (SNMPMgr Component)

Fired before and after a password is hashed.

Syntax

type THashPasswordEvent = procedure (
  Sender: TObject;
  const Password: String;
  AuthAlgorithm: Integer;
  var Hash: String
) of Object;

property OnHashPassword: THashPasswordEvent read FOnHashPassword write FOnHashPassword;

Remarks

SNMPv3 passwords are hashed in order to obtain authentication and encryption keys. This is an expensive operation, and in certain situations it may be preferable to store the hashed passwords externally and supply them on demand.

If a hash is required, the event fires with an empty string in the Hash parameter. In this case, you can choose to supply a value for the hash and stop the component from computing the hash.

The event also fires every time a hash is computed. In this case, the Hash parameter contains the value of the computed hash.

AuthAlgorithm contains either 1 for HMAC-MD5-96, 2 for HMAC-SHA-96 or 3 for HMAC-192-SHA-256

InformRequest Event (SNMPMgr Component)

Fired when an InformRequest packet is received.

Syntax

type TInformRequestEvent = procedure (
  Sender: TObject;
  RequestId: Integer;
  SNMPVersion: Integer;
  const Community: String;
  const User: String;
  SecurityLevel: Integer;
  const SourceAddress: String;
  SourcePort: Integer;
  var ErrorIndex: Integer;
  var ErrorStatus: Integer;
  const ErrorDescription: String;
  var Respond: Boolean
) of Object;

property OnInformRequest: TInformRequestEvent read FOnInformRequest write FOnInformRequest;

Remarks

The user in an InformRequest packet (SNMPv3) must match the user in the User property. If not, the request is rejected, and a BadPacket event is fired before InformRequest is fired.

The list of variables in the SNMP packet, including optional values and types, is provided through the Objects collection. Each object is of type SNMPObject. This type describes the Oid, ObjectType, and Value of each SNMP object. These variables must be copied to another location before the event has completed executing, or they may be overridden by other events.

The SourceAddress and SourcePort parameters show the address and port of the sender as reported by the TCP/IP stack.

The MessageId parameter identifies the received request.

For SNMPv3, the User parameter shows the user that was supplied with the packet. This parameter MUST be used together with the SecurityLevel parameter which shows the level of security in the message.

The SecurityLevel parameter shows whether the request has been authenticated. If SecurityLevel is 0, the request has NOT been authenticated (i.e. the packet signature has not been verified). For an authenticated, non encrypted request, SecurityLevel is 1. For an authenticated and encrypted request, SecurityLevel is 2.

To send a response, the Respond parameter must be set to true. By default, this value is false, which means no response will be sent. The ErrorStatus parameter may also be set to a valid SNMP status code (the default value is 0, which represents no error).

The following is a list of valid SNMP status code values:

The ErrorIndex parameter indicates the index of the first variable (object) that caused an error. The default value is 0.

Variable indexes start with 0. ErrorIndex has no meaning when ErrorStatus is 0 (no error).

PacketTrace Event (SNMPMgr Component)

Fired for every packet sent or received.

Syntax

type TPacketTraceEvent = procedure (
  Sender: TObject;
  Packet: String;
  PacketB: TBytes;
  Direction: Integer;
  const PacketAddress: String;
  PacketPort: Integer
) of Object;

property OnPacketTrace: TPacketTraceEvent read FOnPacketTrace write FOnPacketTrace;

Remarks

The PacketTrace event shows all the packets sent or received by the component.

Packet contains the full contents of the datagram.

Direction shows the direction of the packet: 1 for incoming packets, and 2 for outgoing packets.

In the case of an incoming packet, PacketAddress and PacketPort identify the source of the packet.

In the case of an outgoing packet, PacketAddress and PacketPort identify the destination of the packet.

ReadyToSend Event (SNMPMgr Component)

Fired when the component is ready to send data.

Syntax

type TReadyToSendEvent = procedure (
  Sender: TObject
) of Object;

property OnReadyToSend: TReadyToSendEvent read FOnReadyToSend write FOnReadyToSend;

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a failed DataToSend.

Report Event (SNMPMgr Component)

Fired when a Report packet is received.

Syntax

type TReportEvent = procedure (
  Sender: TObject;
  RequestId: Integer;
  SNMPVersion: Integer;
  const Community: String;
  const User: String;
  SecurityLevel: Integer;
  const SourceAddress: String;
  SourcePort: Integer;
  ErrorIndex: Integer;
  ErrorStatus: Integer;
  const ErrorDescription: String
) of Object;

property OnReport: TReportEvent read FOnReport write FOnReport;

Remarks

For SNMPv3, the User parameter shows the user that was supplied with the packet. This parameter MUST be used together with the SecurityLevel parameter which shows the level of security in the message.

The SecurityLevel parameter shows whether the request has been authenticated. If SecurityLevel is 0, the request has NOT been authenticated (i.e. the packet signature has not been verified). For an authenticated, non encrypted request, SecurityLevel is 1. For an authenticated and encrypted request, SecurityLevel is 2.

The list of variables in the SNMP packet, including optional values and types, is provided through the Objects collection. Each object is of type SNMPObject. This type describes the Oid, ObjectType, and Value of each SNMP object. These variables must be copied to another location before the event has completed executing, or they may be overridden by other events.

The SourceAddress and SourcePort parameters show the address and port of the sender as reported by the TCP/IP stack.

Response Event (SNMPMgr Component)

Fired when a GetResponse packet is received.

Syntax

type TResponseEvent = procedure (
  Sender: TObject;
  RequestId: Integer;
  SNMPVersion: Integer;
  const Community: String;
  const User: String;
  SecurityLevel: Integer;
  const SourceAddress: String;
  SourcePort: Integer;
  ErrorIndex: Integer;
  ErrorStatus: Integer;
  const ErrorDescription: String
) of Object;

property OnResponse: TResponseEvent read FOnResponse write FOnResponse;

Remarks

The ErrorStatus and ErrorIndex parameters contain information about possible errors. ErrorDescription is a textual description of ErrorStatus. This value is parsed directly from the SNMP response, which will be a one-based value, so a value of i here maps to index i-1 in the Objects collection.

The following is a list of valid SNMP status code values:

The ErrorIndex parameter indicates the index of the first variable (object) that caused an error. The default value is 0.

Variable indexes start with 0. ErrorIndex has no meaning when ErrorStatus is 0 (no error).

The list of variables in the SNMP packet, including optional values and types, is provided through the Objects collection. Each object is of type SNMPObject. This type describes the Oid, ObjectType, and Value of each SNMP object. These variables must be copied to another location before the event has completed executing, or they may be overridden by other events.

The SourceAddress and SourcePort parameters show the address and port of the sender as reported by the TCP/IP stack.

Trap Event (SNMPMgr Component)

Fired when a SNMP trap packet is received.

Syntax

type TTrapEvent = procedure (
  Sender: TObject;
  RequestId: Integer;
  SNMPVersion: Integer;
  const Community: String;
  const User: String;
  SecurityLevel: Integer;
  const TrapOID: String;
  TimeStamp: Int64;
  const SourceAddress: String;
  SourcePort: Integer
) of Object;

property OnTrap: TTrapEvent read FOnTrap write FOnTrap;

Remarks

The SNMPTrapMgr component should normally be used to receive traps, since it was designed and contains functionality specifically for that purpose. The SNMPMgr component can only receive traps from the agent that it is has most recently discovered with the Discover method.

The TrapOID and TimeStamp parameters contain the Trap OID and TimeStamp. In the case of an SNMPv1 trap, there are two possible scenarios:

First, if the enterprise of the trap is "1.3.6.1.6.3.1.1.5", TrapOID will be a concatenation of TrapEnterprise and GenericTrap + 1. For instance a TrapOID of "1.3.6.1.6.3.1.1.5.5" has a TrapEnterprise of "1.3.6.1.6.3.1.1.5" and a GenericTrap of "4".

Second, In all other cases TrapOID will be a concatenation of the values for TrapEnterprise, GenericTrap, and SpecificTrap, separated by '.'.

For SNMPv2 and above, they are read from the variable-value list (if available).

For SNMPv3, the User parameter shows the user that was supplied with the packet. This parameter MUST be used together with the SecurityLevel parameter which shows the level of security in the message.

The SecurityLevel parameter shows whether the request has been authenticated. If SecurityLevel is 0, the request has NOT been authenticated (i.e. the packet signature has not been verified). For an authenticated, non encrypted request, SecurityLevel is 1. For an authenticated and encrypted request, SecurityLevel is 2.

The SNMPMgr component is limited to accepting authenticated traps only for the user specified in User and Password and from the engine specified in RemoteEngineId with time parameters in RemoteEngineBoots and RemoteEngineTime (usually this is the SNMP engine discovered through the last call to Discover). If authenticated traps come from a different engine, or for a different user, they are ignored, and a BadPacket event is fired instead.

The list of variables in the SNMP packet, including optional values and types, is provided through the Objects collection. Each object is of type SNMPObject. This type describes the Oid, ObjectType, and Value of each SNMP object. These variables must be copied to another location before the event has completed executing, or they may be overridden by other events.

The SourceAddress and SourcePort parameters show the address and port of the sender as reported by the TCP/IP stack.

SNMPObject Type

The current SNMP object.

Remarks

This type defines an SNMP object. Each object has an Oid, ObjectType, and Value. These values are populated by the component when incoming packets are received. You may use these fields to define objects to be used in outgoing packets.

Fields

Constructors

constructor Create();

constructor Create(valOid: String);

constructor Create(valOid: String; valValue: TBytes);

Config Settings (SNMPMgr Component)

The component accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

SNMPManager Config Settings

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (SNMPMgr Component)

SNMPMgr Errors

	201   Timeout.
	301   Bad Object Index when accessing the Obj* properties. Timeout when performing an operation. Check the error description for details.
	302   Value exceeds maximum number of objects allowed.
	303   The value must be an IP address in dotted format.
	305   Unsupported SNMP version.
	306   Unknown PDU type.
	307   The component is busy performing the current action.
	308   Verification failed.
	309   Missing password for Verification.
	310   Missing signature.
	311   Missing remote time.
	312   Missing timeout value.
	313   Decryption Failed.
	314   Missing password for decryption.
	315   Not encrypted.
	316   Security model not supported.
	317   Defective packet
	318   Not from bound point.
	319   Operation not permitted in current role.
	320   Bad packet.
	321   Message not authenticated.
	322   No such oid.
	323   Missing privacy parameter.
	324   Bad engine id.
	325   Bad time frame.
	326   Bad user name.
	327   Security level was not accepted.
	328   Discovery failed.
	329   Incorrect key length.
	330   No authentication password supplied.
	333   Returned OID was out of range. This is applicable only when WalkInsideRange is set to true.

The component may also return one of the following error codes, which are inherited from other components.

UDP Errors

	104   UDP is already Active.
	106   You cannot change the LocalPort while the component is Active.
	107   You cannot change the LocalHost at this time. A connection is in progress.
	109   The component must be Active for this operation.
	112   Cannot change MaxPacketSize while the component is Active.
	113   Cannot change ShareLocalPort option while the component is Active.
	114   Cannot change RemoteHost when UseConnection is set and the component Active.
	115   Cannot change RemotePort when UseConnection is set and the component is Active.
	116   RemotePort can't be zero when UseConnection is set. Please specify a valid service port number.
	117   Cannot change UseConnection while the component is Active.
	118   Message can't be longer than MaxPacketSize.
	119   Message too short.
	434   Unable to convert string to selected CodePage

SSL Errors

	270   Cannot load specified security library.
	271   Cannot open certificate store.
	272   Cannot find specified certificate.
	273   Cannot acquire security credentials.
	274   Cannot find certificate chain.
	275   Cannot verify certificate chain.
	276   Error during handshake.
	280   Error verifying certificate.
	281   Could not find client certificate.
	282   Could not find server certificate.
	283   Error encrypting data.
	284   Error decrypting data.

TCP/IP Errors

	10004   [10004] Interrupted system call.
	10009   [10009] Bad file number.
	10013   [10013] Access denied.
	10014   [10014] Bad address.
	10022   [10022] Invalid argument.
	10024   [10024] Too many open files.
	10035   [10035] Operation would block.
	10036   [10036] Operation now in progress.
	10037   [10037] Operation already in progress.
	10038   [10038] Socket operation on non-socket.
	10039   [10039] Destination address required.
	10040   [10040] Message too long.
	10041   [10041] Protocol wrong type for socket.
	10042   [10042] Bad protocol option.
	10043   [10043] Protocol not supported.
	10044   [10044] Socket type not supported.
	10045   [10045] Operation not supported on socket.
	10046   [10046] Protocol family not supported.
	10047   [10047] Address family not supported by protocol family.
	10048   [10048] Address already in use.
	10049   [10049] Can't assign requested address.
	10050   [10050] Network is down.
	10051   [10051] Network is unreachable.
	10052   [10052] Net dropped connection or reset.
	10053   [10053] Software caused connection abort.
	10054   [10054] Connection reset by peer.
	10055   [10055] No buffer space available.
	10056   [10056] Socket is already connected.
	10057   [10057] Socket is not connected.
	10058   [10058] Can't send after socket shutdown.
	10059   [10059] Too many references, can't splice.
	10060   [10060] Connection timed out.
	10061   [10061] Connection refused.
	10062   [10062] Too many levels of symbolic links.
	10063   [10063] File name too long.
	10064   [10064] Host is down.
	10065   [10065] No route to host.
	10066   [10066] Directory not empty
	10067   [10067] Too many processes.
	10068   [10068] Too many users.
	10069   [10069] Disc Quota Exceeded.
	10070   [10070] Stale NFS file handle.
	10071   [10071] Too many levels of remote in path.
	10091   [10091] Network subsystem is unavailable.
	10092   [10092] WINSOCK DLL Version out of range.
	10093   [10093] Winsock not loaded yet.
	11001   [11001] Host not found.
	11002   [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
	11003   [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
	11004   [11004] Valid name, no data record (check DNS setup).