tnet.go - tordam - A library for peer discovery inside the Tor network
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       tnet.go (1291B)
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            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 }