net.go (1291B)
1 // Copyright (c) 2017-2021 Ivan Jelincic <parazyd@dyne.org> 2 // 3 // This file is part of tordam 4 // 5 // This program is free software: you can redistribute it and/or modify 6 // it under the terms of the GNU Affero General Public License as published by 7 // the Free Software Foundation, either version 3 of the License, or 8 // (at your option) any later version. 9 // 10 // This program is distributed in the hope that it will be useful, 11 // but WITHOUT ANY WARRANTY; without even the implied warranty of 12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 // GNU Affero General Public License for more details. 14 // 15 // You should have received a copy of the GNU Affero General Public License 16 // along with this program. If not, see <https://www.gnu.org/licenses/>. 17 18 package tordam 19 20 import "net" 21 22 // GetAvailableListener is a helper function to return a *net.TCPAddr on some 23 // port that is available for listening on the system. It uses the :0 port 24 // which the kernel utilizes to return a random available port. 25 func GetAvailableListener() (*net.TCPAddr, error) { 26 addr, err := net.ResolveTCPAddr("tcp4", "localhost:0") 27 if err != nil { 28 return nil, err 29 } 30 31 l, err := net.ListenTCP("tcp4", addr) 32 if err != nil { 33 return nil, err 34 } 35 defer l.Close() 36 return l.Addr().(*net.TCPAddr), nil 37 }