参考：/m0_37567543/article/details/78687599
/brandon/article/details/51811914
Asterisk是一个相对成熟的VOIP电话的服务器，可以通过下载安装包或apt-get方式进行安装。建议使用apt-get方式，因为asterisk需要依赖很多东西，通过apt-get安装可以直接将需要的库等都安装好。
由于设备要注册到asterisk服务器，故安装时需要将虚拟机配置成桥接网络模式，配置方法可自行百度。
1、sudo apt-get install asterisk
2、安装好后进行文件配置，首先配置用户信息sip.conf文件(添加SIP账号)
vi /etc/asterisk/sip.conf
[general]
context = default
tcpbindaddr = 0.0.0.0
tcpenable = yes
videosupport=always
[1001]
videosupport=always
type = friend
username=1001
secret = 1001
host = dynamic
canreinvite = no
dtmfmode = rfc2833
mailbox = mailbox
transport = udp
nat=yes
videosupport=always
maxcallbitrate=384
canreinvite=no
disallow=all
allow = ulaw
allow=alaw
allow=h263
allow=h264
[1002]
videosupport=always
type = friend
username=1002
secret = 1002
host = dynamic
canreinvite = no
dtmfmode = rfc2833
mailbox = mailbox
transport = udp
nat=yes
videosupport=always
maxcallbitrate=384
canreinvite=no
disallow=all
allow = ulaw
allow=alaw
allow=h263
allow=h264
3、配置每个用户打电话的相关策略，即配置extension.conf文件
vi /etc/asterisk/extensions.conf
[general]
static=yes
writeprotect=no
[default]
exten => 1001,1,Dial(SIP/1001)
exten => 1002,1,Dial(SIP/1002)
4、重启asterisk
/etc/init.d/asterisk restart
