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net.go
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net.go
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package net
import (
"errors"
"fmt"
"net"
"strconv"
"strings"
)
// Listen takes addr:portmin-portmax and binds to the first available port
// Example: Listen("localhost:5000-6000", fn)
func Listen(addr string, fn func(string) (net.Listener, error)) (net.Listener, error) {
// host:port || host:min-max
parts := strings.Split(addr, ":")
//
if len(parts) < 2 {
return fn(addr)
}
// try to extract port range
ports := strings.Split(parts[len(parts)-1], "-")
// single port
if len(ports) < 2 {
return fn(addr)
}
// we have a port range
// extract min port
min, err := strconv.Atoi(ports[0])
if err != nil {
return nil, errors.New("unable to extract port range")
}
// extract max port
max, err := strconv.Atoi(ports[1])
if err != nil {
return nil, errors.New("unable to extract port range")
}
// set host
host := parts[:len(parts)-1]
// range the ports
for port := min; port <= max; port++ {
// try bind to host:port
ln, err := fn(fmt.Sprintf("%s:%d", host, port))
if err == nil {
return ln, nil
}
// hit max port
if port == max {
return nil, err
}
}
// why are we here?
return nil, fmt.Errorf("unable to bind to %s", addr)
}