在2021年用电话线拨号上网管理服务器
电话线供电
没有电话交换机。直接用电话线把两个MODEM接起来(Dry line)是不工作的。
据说电话线上的电压:
- 没有电话呼入呼出 20V
- 有电话呼入’RING’: 20-25Hz, 50-120Vpp (也有说48V)
- 接听状态 10V
电话交换机的作用是,制造一个’RING’信号,让MODEM振铃。MODEM会在串口上打出RING
字样。
+ | | -
GREEN----------+---||||---/\/\/--+-------------RED
| | | R |
| 9 to 24V |
| |
+---||------------+
C .47uF
RED-----------------------------------------------GREEN
手边刚好翻出一个9V电池。用两个曲别针当电极。
并把家里墙上的电话插座拆了。搭出了下面的东西: (Dell RD02-D400)
直接通信
客户端:
picocom -b 115200 /dev/tty.usbmodem2
ATX0 #忽略拨号音
ATDT123123 #随便拨一个号, ATD也行, ATD100, ATDT100都可以
(服务器)局端:
picocom -b 115200 /dev/ttyACM0
ATA #接电话, Answer
然后两只🐱就会协商,提示
CONNECT 115200
然后链路就通了,继续在picocom里打字,对端就会显示
进一步: getty
在服务器(局端)按C-a C-q
退出picocom
systemctl start getty@ttyACM0.service #在/lib/systemd/system/getty\@.service 里可以看到,实际上是/sbin/agetty
这时,在客户端就出现了
login:
可以动手了。
有趣的是:
$ w
USER TTY FROM LOGIN@ IDLE WHAT
scateu ttyACM0 .....
无人值守: mgetty
由于我们没有振铃信号,无法出现RING
字样。因此让它自动回复ATA
来强制接听。(不是好的选择)
sudo /usr/sbin/mgetty -D -s 115200 -m '"" ATA' /dev/ttyACM0 #在客户端ATD指令之后再敲回车
tail -f /var/log/mgetty.ttyACM0
See also
- 据说用
AT+MS=V32
设置波特率为9600,Skype上也很稳 - Dialup modem trying to train on VoIP - YouTube
- Using a VOIP Line for DUN – Albal’s Blog
- Opera singers dubbed with dial up modems - YouTube
- 56k and 33.6k Modems Connecting to Each Other with no Phone Service - YouTube
- NO CARRIER - Wikipedia
- Null modem - Wikipedia
- How to Get Emergency Power From a Phone Line : 5 Steps - Instructables
- Dry loop - Wikipedia
- Modem-HOWTO: Appendix F: Connecting 2 Modems Directly Back-to-Back (Leased Lines).
- Connecting two computers using their modems, without a telephone line
- Direct Connecting Two (old Fashioned) Modems or Telephones. : 5 Steps - Instructables
- telephone - Wiring up old phone ringer to arduino - Electrical Engineering Stack Exchange
- Ring signal generator - YouTube
- mgetty Attachment 1701152 Details for Bug 1856765 – Patch sent upstream
- Dial up server - Doge Microsystems
- Setup your own Dial-Up Networking Server with real hardware! - YouTube
- Dial-up pool - Doge Microsystems
- Build Your Own Dial-Up ISP – Now With Modem Pool! | Hackaday
- Setting up my own Dialup Internet connection using a Mac, a PC, and an eBay PBX - YouTube
- Direct connection between two modems for routing. - Ars Technica OpenForum
- Leased line Mini HOWTO: Modem
- Conexant DGC-USB
- 搜索关键词 “Dial in” “Dial up” “Phone Line Simulator” “Dry line” “Dry Pair” “Wet line” “leased line”
- “modem over voip” “modem over vonage” “modem over skype”
- Minimodem - http://www.whence.com/minimodem/