Learning Golang and Network Programming

This blog contains notes on mostly NTP Learning in conjunction with reading the ntpc.go module in this Github repo vladimirvivien/go-networking.

Intro

I have been starting to learn Golang and wanted to start learning why Golang is good for Network Programming. After searching, I found this repo vladimirvivien/go-networking. Here are my notes from reading the ntpc.go and ntps.go modules, mostly the former, in this repo.

ntpc.go

First, the Packt book is no longer available, so I thought to read ntpc.go.

Learning about Go, this module starts with:

var host string
flag.StringVar(&host, "e", "us.pool.ntp.org:123", "NTP host")
flag.Parse()

Here flag.StringVar is intialized to the address of a pointer, with the default value of the 3rd arg, func StringVar(p *string, name string, value string, usage string)

Usage:

// uses default
go run ntpc.go

// uses ntp server from ntps.go
go run ntps.go
go run ntpc.go -e localhost:1123

Golang net pkg

The net pkg is used to create a UDP object, establish a connect then send a request and response. I looked up the us.pool.ntp.org IP information to compare to the Golang objects:

$ nslookup us.pool.ntp.org
Server:		192.168.1.1
Address:	192.168.1.1#53

Non-authoritative answer:
Name:	us.pool.ntp.org
Address: 70.35.196.28
Name:	us.pool.ntp.org
Address: 168.61.215.74
Name:	us.pool.ntp.org
Address: 216.229.4.69
Name:	us.pool.ntp.org

Address: 66.151.147.38

The first Server address is our private network DNS address with th

192.168.0.0/16 Address for private networks (intranets). Such addresses never appear on the public Internet.

References

https://timetoolsltd.com/ntp/ntp-client/