echoRequest

​
Provides lower-level access to the ICMP Echo Request infrastructure used by the hs.network.ping module. In general, you should not need to use this module directly unless you have specific requirements not met by the hs.network.ping module and the hs.network.ping object methods.
This module is based heavily on Apple's SimplePing sample project which can be found at https://developer.apple.com/library/content/samplecode/SimplePing/Introduction/Intro.html.
When a callback function argument is specified as an ICMP table, the Lua table returned will contain the following key-value pairs:
checksum - The ICMP packet checksum used to ensure data integrity.
code - ICMP Control Message Code. This should always be 0 unless the callback has received a "receivedUnexpectedPacket" message.
identifier - The ICMP packet identifier. This should match the results of hs.network.ping.echoRequest:identifier unless the callback has received a "receivedUnexpectedPacket" message.
payload - A string containing the ICMP payload for this packet. The default payload has been constructed to cause the ICMP packet to be exactly 64 bytes to match the convention for ICMP Echo Requests.
sequenceNumber - The ICMP Sequence Number for this packet.
type - ICMP Control Message Type. Unless the callback has received a "receivedUnexpectedPacket" message, this will be 0 (ICMPv4) or 129 (ICMPv6) for packets we receive and 8 (ICMPv4) or 128 (ICMPv6) for packets we send.
_raw - A string containing the ICMP packet as raw data.
In cases where the callback receives a "receivedUnexpectedPacket" message because the packet is corrupted or truncated, this table may only contain the _raw field.
API Overview
Constructors - API calls which return an object, typically one that offers API methods
​echoRequest​
Methods - API calls which can only be made on an object returned by a constructor
​acceptAddressFamily​
​hostAddress​
​hostAddressFamily​
​hostName​
​identifier​
​isRunning​
​nextSequenceNumber​
​seeAllUnexpectedPackets​
​sendPayload​
​setCallback​
​start​
​stop​
API Documentation
Constructors
​echoRequest​
Signature
hs.network.ping.echoRequest.echoRequest(server) -> echoRequestObject
Type
Constructor
Description
Creates a new ICMP Echo Request object for the server specified.
Parameters
server - a string containing the hostname or ip address of the server to communicate with. Both IPv4 and IPv6 style addresses are supported.
Returns
an echoRequest object
Notes
This constructor returns a lower-level object than the hs.network.ping.ping constructor and is more difficult to use. It is recommended that you use this constructor only if hs.network.ping.ping is not sufficient for your needs.
Methods
​acceptAddressFamily​
| Signature | hs.network.ping.echoRequest:acceptAddressFamily([family]) -> echoRequestObject | current value | | -----------------------------------------------------|---------------------------------------------------------------------------------------------------------| | Type | Method | | Description | Get or set the address family the echoRequestObject should communicate with. | | Parameters |
family - an optional string, default "any", which specifies the address family used by this object. Valid values are "any", "IPv4", and "IPv6".
| | Returns |
if an argument is provided, returns the echoRequestObject, otherwise returns the current value.
| | Notes |
Setting this value to "IPv6" or "IPv4" will cause the echoRequestObject to attempt to resolve the server's name into an IPv6 address or an IPv4 address and communicate via ICMPv6 or ICMP(v4) when the hs.network.ping.echoRequest:start method is invoked. A callback with the message "didFail" will occur if the server could not be resolved to an address in the specified family.
If this value is set to "any", then the first address which is discovered for the server's name will determine whether ICMPv6 or ICMP(v4) is used, based upon the family of the address.
|
​hostAddress​
| Signature | hs.network.ping.echoRequest:hostAddress() -> string | false | nil | | -----------------------------------------------------|---------------------------------------------------------------------------------------------------------| | Type | Method | | Description | Returns a string representation for the server's IP address, or a boolean if address resolution has not completed yet. | | Parameters |
None
| | Returns |
If the object has been started and address resolution has completed, then the string representation of the server's IP address is returned.
If the object has been started, but resolution is still pending, returns a boolean value of false.
If the object has not been started, returns nil.
|
​hostAddressFamily​
Signature
hs.network.ping.echoRequest:hostAddressFamily() -> string
Type
Method
Description
Returns the host address family currently in use by this echoRequestObject.
Parameters
None
Returns
a string indicating the IP address family currently used by this echoRequestObject. It will be one of the following values:
"IPv4" - indicates that ICMP(v4) packets are being sent and listened for.
"IPv6" - indicates that ICMPv6 packets are being sent and listened for.
"unresolved" - indicates that the echoRequestObject has not been started or that address resolution is still in progress.
​hostName​
Signature
hs.network.ping.echoRequest:hostName() -> string
Type
Method
Description
Returns the name of the target host as provided to the echoRequestObject's constructor
Parameters
None
Returns
a string containing the hostname as specified when the object was created.
​identifier​
Signature
hs.network.ping.echoRequest:identifier() -> integer
Type
Method
Description
Returns the identifier number for the echoRequestObject.
Parameters
None
Returns
an integer specifying the identifier which is embedded in the ICMP packets this object sends.
Notes
ICMP Echo Replies which include this identifier will generate a "receivedPacket" message to the object callback, while replies which include a different identifier will generate a "receivedUnexpectedPacket" message.
​isRunning​
Signature
hs.network.ping.echoRequest:isRunning() -> boolean
Type
Method
Description
Returns a boolean indicating whether or not this echoRequestObject is currently listening for ICMP Echo Replies.
Parameters
None
Returns
true if the object is currently listening for ICMP Echo Replies, or false if it is not.
​nextSequenceNumber​
Signature
hs.network.ping.echoRequest:nextSequenceNumber() -> integer
Type
Method
Description
The sequence number that will be used for the next ICMP packet sent by this object.
Parameters
None
Returns
an integer specifying the sequence number that will be embedded in the next ICMP message sent by this object when hs.network.ping.echoRequest:sendPayload is invoked.
Notes
ICMP Echo Replies which are expected by this object should always be less than this number, with the caveat that this number is a 16-bit integer which will wrap around to 0 after sending a packet with the sequence number 65535.
Because of this wrap around effect, this module will generate a "receivedPacket" message to the object callback whenever the received packet has a sequence number that is within the last 120 sequence numbers we've sent and a "receivedUnexpectedPacket" otherwise.
Per the comments in Apple's SimplePing.m file: Why 120? Well, if we send one ping per second, 120 is 2 minutes, which is the standard "max time a packet can bounce around the Internet" value.
​seeAllUnexpectedPackets​
| Signature | hs.network.ping.echoRequest:seeAllUnexpectedPackets([state]) -> boolean | echoRequestObject | | -----------------------------------------------------|---------------------------------------------------------------------------------------------------------| | Type | Method | | Description | Get or set whether or not the callback should receive all unexpected packets or only those which carry our identifier. | | Parameters |
state - an optional boolean, default false, specifying whether or not all unexpected packets or only those which carry our identifier should generate a "receivedUnexpectedPacket" callback message.
| | Returns |
if an argument is provided, returns the echoRequestObject; otherwise returns the current value
| | Notes |
The nature of ICMP packet reception is such that all listeners receive all ICMP packets, even those which belong to another process or echoRequestObject.
By default, a valid packet (i.e. with a valid checksum) which does not contain our identifier is ignored since it was not intended for our receiver. Only corrupt or packets with our identifier but that were otherwise unexpected will generate a "receivedUnexpectedPacket" callback message.
This method optionally allows the echoRequestObject to receive all incoming packets, even ones which are expected by another process or echoRequestObject.
If you wish to examine ICMPv6 router advertisement and neighbor discovery packets, you should set this property to true. Note that this module does not provide the necessary tools to decode these packets at present, so you will have to decode them yourself if you wish to examine their contents.
|
​sendPayload​
| Signature | hs.network.ping.echoRequest:sendPayload([payload]) -> echoRequestObject | false | nil | | -----------------------------------------------------|---------------------------------------------------------------------------------------------------------| | Type | Method | | Description | Sends a single ICMP Echo Request packet. | | Parameters |
payload - an optional string containing the data to include in the ICMP Echo Request as the packet payload.
| | Returns |
If the object has been started and address resolution has completed, then the ICMP Echo Packet is sent and this method returns the echoRequestObject
If the object has been started, but resolution is still pending, the packet is not sent and this method returns a boolean value of false.
If the object has not been started, the packet is not sent and this method returns nil.
| | Notes |
By convention, unless you are trying to test for specific network fragmentation or congestion problems, ICMP Echo Requests are generally 64 bytes in length (this includes the 8 byte header, giving 56 bytes of payload data). If you do not specify a payload, a default payload which will result in a packet size of 64 bytes is constructed.
|
​setCallback​
Signature
hs.network.ping.echoRequest:setCallback(fn) -> echoRequestObject
Type
Method
Description
Set or remove the object callback function
Parameters
fn - a function to set as the callback function for this object, or nil if you wish to remove any existing callback function.
Returns
the echoRequestObject
Notes
The callback function should expect between 3 and 5 arguments and return none. The possible arguments which are sent will be one of the following:
​start​
Signature
hs.network.ping.echoRequest:start() -> echoRequestObject
Type
Method
Description
Start the echoRequestObject by resolving the server's address and start listening for ICMP Echo Reply packets.
Parameters
None
Returns
the echoRequestObject
​stop​
Signature
hs.network.ping.echoRequest:stop() -> echoRequestObject
Type
Method
Description
Stop listening for ICMP Echo Reply packets with this object.
Parameters
None
Returns
the echoRequestObject