Checking for open ports in go lang
I had to create a periodic status check for an open port on a specific host for a service I was creating recently. The status check has to work for both the localhost in development and also on the remote host.
Using the [net][net pkg] package in Go I was able to come up with the following snippet for testing the localhost port:
package main
import (
"fmt"
"net"
)
func main() {
l, err := net.Listen("tcp", ":" + port)
defer l.Close()
if err != nil {
// Log or report the error here
fmt.Printf("Error: %s\n", err)
}
}We use [Listen][net pkg Listen] above as it works for localhost only.
For testing the remote port, we can use [DialTimeout][net pkg DialTimeout] as it accepts a custom timeout parameter, which we can use to check for timeout errors:
package main
import (
"fmt"
"net"
"time"
)
func main() {
// host -> the remote host
// timeoutSecs -> the timeout value
conn, err := net.DialTimeout("tcp", host, time.Duration(timeoutSecs)*time.Second)
defer conn.Close()
if err, ok := err.(*net.OpError); ok && err.TimeOut() {
fmt.Printf("Timeout error: %s\n", err)
return
}
if err != nil {
// Log or report the error here
fmt.Printf("Error: %s\n", err)
return
}
}