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// Copyright 2016 Cong Ding
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package stun
import (
"errors"
"net"
"strconv"
)
// Client is a STUN client, which can be set STUN server address and is used
// to discover NAT type.
type Client struct {
serverAddr string
softwareName string
conn net.PacketConn
logger *Logger
}
// NewClient returns a client without network connection. The network
// connection will be build when calling Discover function.
func NewClient() *Client {
c := new(Client)
c.SetSoftwareName(DefaultSoftwareName)
c.logger = NewLogger()
return c
}
// NewClientWithConnection returns a client which uses the given connection.
// Please note the connection should be acquired via net.Listen* method.
func NewClientWithConnection(conn net.PacketConn) *Client {
c := new(Client)
c.conn = conn
c.SetSoftwareName(DefaultSoftwareName)
c.logger = NewLogger()
return c
}
// SetVerbose sets the client to be in the verbose mode, which prints
// information in the discover process.
func (c *Client) SetVerbose(v bool) {
c.logger.SetDebug(v)
}
// SetVVerbose sets the client to be in the double verbose mode, which prints
// information and packet in the discover process.
func (c *Client) SetVVerbose(v bool) {
c.logger.SetInfo(v)
}
// SetServerHost allows user to set the STUN hostname and port.
func (c *Client) SetServerHost(host string, port int) {
c.serverAddr = net.JoinHostPort(host, strconv.Itoa(port))
}
// SetServerAddr allows user to set the transport layer STUN server address.
func (c *Client) SetServerAddr(address string) {
c.serverAddr = address
}
// SetSoftwareName allows user to set the name of the software, which is used
// for logging purpose (NOT used in the current implementation).
func (c *Client) SetSoftwareName(name string) {
c.softwareName = name
}
// Discover contacts the STUN server and gets the response of NAT type, host
// for UDP punching.
func (c *Client) Discover() (NATType, *Host, error) {
if c.serverAddr == "" {
c.SetServerAddr(DefaultServerAddr)
}
serverUDPAddr, err := net.ResolveUDPAddr("udp", c.serverAddr)
if err != nil {
return NATError, nil, err
}
// Use the connection passed to the client if it is not nil, otherwise
// create a connection and close it at the end.
conn := c.conn
if conn == nil {
conn, err = net.ListenUDP("udp", nil)
if err != nil {
return NATError, nil, err
}
defer conn.Close()
}
return c.discover(conn, serverUDPAddr)
}
// Keepalive sends and receives a bind request, which ensures the mapping stays open
// Only applicable when client was created with a connection.
func (c *Client) Keepalive() (*Host, error) {
if c.conn == nil {
return nil, errors.New("no connection available")
}
if c.serverAddr == "" {
c.SetServerAddr(DefaultServerAddr)
}
serverUDPAddr, err := net.ResolveUDPAddr("udp", c.serverAddr)
if err != nil {
return nil, err
}
resp, err := c.test1(c.conn, serverUDPAddr)
if err != nil {
return nil, err
}
if resp == nil || resp.packet == nil {
return nil, errors.New("failed to contact")
}
return resp.mappedAddr, nil
}
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