packer-plugin-xenserver/builder/xenserver/find_port.go

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package xenserver
import (
"fmt"
"log"
"net"
)
// FindPort finds and starts listening on a port in the range [portMin, portMax]
// returns the listener and the port number on success, or nil, 0 on failure
func FindPort(portMin uint, portMax uint) (net.Listener, uint) {
log.Printf("Looking for an available port between %d and %d", portMin, portMax)
for port := portMin; port <= portMax; port++ {
log.Printf("Trying port: %d", port)
l, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
if err == nil {
return l, port
} else {
log.Printf("Port %d unavailable: %s", port, err.Error())
}
}
return nil, 0
}