The ping networking utility (backronym Packet InterNet Groper) [1, 2, 3] is a common tool used to determine network delay and whether a host is active at an IP address [4]. Ping sends an Internet Control Message Packet (ICMP) [5] to a host as an echo request, which then receives a response from the remote host. Ping sends data about the time and the host sends the data back – to put it at its simplest, plainest explanation.

Ping is popular with admins around the world, however, the ping utility is not without problems. For instance, ping can be used to send a packet storm to overload and crash a host system – a denial-of-service (DOS) attack called a ping flood. Some sites simply do not respond to ping requests, and some firewalls block the ICMP packets sent by the ping utility.

A problem I faced was the need for ping functionality, but without sending packets of data through the network. One of the best things about being a software development engineer is that, for interesting problems, it only takes a little creativity to find a solution. Driven by the need, I created my own network utility.

My requirements for this utility were:

• No data payload is sent or received, to avoid network congestion.
• Ability to check that both a host and the ports are alive and available
• Able to report the time to reach a host connect and disconnect
• Available to run on multiple platforms, in this case, Windows, macOS, and Linux
• Support for both Internet Protocol version 4 and version 6 addresses
• Parameters and reporting similar to ping – a familiar look and feel

With these objectives in mind, I created Zing. The name Zing is an acronym for Zero packet pING. I wanted the utility to have a name that sounds like ping, but I also liked the reference to zinging a system, much as an improv comic will zing a person in humor.

Application

Zing is implemented as both a command-line interface utility and a library function in Java. Using Java achieves cross-platform availability. Then, for each platform, I created a launch app (or kicker app) to run the Zing network utility.

Zing works by a simple approach: Measure the amount of time to connect and disconnect from specified ports for some limit to the number of operations. The idea behind Zing is not uniquely mine. I have read source code in network applications and libraries that takes a similar approach. Unlike the other tools I've seen, though, Zing is designed to look and operate more like ping.

This idea of connecting, binding, and disconnecting avoids sending any ICMP packets or other data. Zing simply requests to connect, connects, then disconnects. More measurements of each op give greater accuracy in the network timing. During this process, a host and port are determined to be reachable, available, and responding. Also, in some cases, a connection request can pass through a firewall to a remote host and port.

The host system will only see several connection requests, connects, and disconnects. In short, Zing looks like any other Internet application because it is not sending an ICMP packet.

Operation

Zing is implemented in Java and is a command line interface utility application. The Java class source code is approximately 400 lines, of which there are approximately 250 lines of code. Zing uses only JDK libraries and packages and implements some helpful internal methods. All methods and attributes are static, and the Java class does not sub-class a parent class explicitly (all Java classes are a sub-class of java.lang.Object implicitly), and Zing is a self-contained program utility using only the libraries in the JDK within the Java class.

The Zing network utility has the following command line parameters:

zing [-4 | -6] [-c count] [-op ops] flfl
[-p ports] [-t timeout] [-h] hostname

Each Zing network utility parameter is:

-4:  TCP IP address version 4 (IPv4)
-6:  TCP IP address version 6 (IPv6).
-c:  the count of the number of operations per port.
-op: the number of ops per count.
-p:  a list of ports to be used by the Zing network utility.
-t:  the timeout waiting for a host response.
-h:  a request for help, giving the Zing CLI parameters.

The hostname can be the host system IP address or the host system name. The default values for the command line interface parameters for the Zing network utility are:

zing -4 -c 4 -op 4 -p 80,443 -t 4000 host

These default command line interface parameters are Internet Protocol version 4 (IPv4), with a count of four times for each port, and the default ports are port 80 for the HTTP protocol and 443 for the HTTPS protocol. The default timeout is 4,000 milliseconds or four seconds. The host you wish to zing is a required parameter with no default.

Design

The Zing network utility is a single Java class with static methods and attributes. The 12 static attributes are used by Zing and are initialized to the default values. The 10 static attributes as Java code fragments are (see Table 1 for descriptions):

boolean     hostFlag  = true;
boolean     tcp4Flag  = true;
InetAddress inet_addr = null;
int         count     = 4;
int         limit     = 4;
int         timeout   = 4000;
Integer[]   ports     = flfl
    new Integer[]{ 80, 443 };
String      host      = "localhost";
String      hostAddr  = "";
String      hostName  = "";

The Zing network utility also has 10 specific static methods for the operation of the utility. The 10 methods are shown in Listing 1. See Table 2 for a description of these Zing methods.

01 double          doZingToHost(final String host, final int port)
02 InetAddress  getHostAddrName(final String host)
03 Inet4Address     getIPv4Addr(final String hostName)
04 Inet6Address     getIPv6Addr(final String hostName)
05 double          getTotalTime(final double totalTime,
06                              final int portsLength, final int limit)
07 void main(final String[] args)
08 void processArgs(final String[] args)
09 void report(final double time)
10 void stddev(final double average, final double[] values)
11 void usage()