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Serial Proxy

serial-proxy is a Linux daemon that will proxy data from any number of serial devices (RS232) to their respective pseudo-terminals (virtual serial ports). This allows more than one application to receive raw data from a single serial port and pretend it is reading from a physical device.

/dev/ttyS1 (Garmin GPS)  /dev/ttyUSB1 (Temperature readings)
     |                         |
    / \                       /|\
   /   \                     / | \
  /     \                   /  |  \
App1   App2              App3 App4 App5

This is a C port of rkubik/serial-proxy.

Features

  • C
  • Less than 100 KB on disk
  • Dependency free
  • Simple INI configuration
  • Linux only (pull requests welcome for other platforms)
  • Virtual writers
  • Event-driven, single process

Installation

git clone ...
cd serial-proxy-c
mkdir build
cd build

cmake ..
make
make install

debuild -us -uc -b
dpkg -i ../serial-proxy_*.deb

Debugging:

dpkg -i ../serial-proxy-dbg_*.deb

Usage

serial-proxy is driven by two INI config files:

  1. sproxy.ini - system configuration (optional). Can be set via -c command-line argument. The systemd service file will set -c to /etc/serial-proxy/sproxy.ini.

Example:

[logging]
loglevel = debug
syslog-enabled = no
logfile = /var/log/sproxy.log

[system]
pidfile = /var/run/sproxyd.pid
serial-configfile = /etc/serial-proxy/serial.ini
hz = 10
reconnect-interval = 5000
  1. serial.ini - serial port configuration. Set via system configuration file using serial-configfile. Default: serial.ini.

Example:

[/dev/ttyS5]
baudrate = 38400
virtuals = a b c
writer = a

[/dev/ttyS6]
baudrate = 9600
virtuals = d e f

The serial configuration file above will attempt to open two physical devices /dev/ttyS5 and /dev/ttyS6. /dev/ttyS5 will proxy data two three virtual devices /dev/ttyS5.a, /dev/ttyS5.b, and /dev/ttyS5.c. Other applications may open and read and write to these virtual devices as if they are physical devices. Only one virtual device is allowed to write to the master (physical) at a time.

Example

# Verify physical serial port is writing data
$ cat /dev/ttyUSB0
�~��3�0���0���������������������^C

# Create system config pointing to serial configuration
$ cat >/etc/serial-proxy/sproxy.ini <<- EOM
[system]
serial-configfile = /etc/serial-proxy/serial.ini
EOM

# Create configuration file for serial port
$ cat > /etc/serial-proxy/serial.ini <<- EOM
[/dev/ttyUSB0]
virtuals = app1,app2
baudrate = 9600
EOM

# Start serial-proxy
$ systemctl start serial-proxy
# Or
$ sproxyd -c /etc/serial-proxy/sproxy.ini

# Check existence of virtual serial ports
$ ls -la /dev/ttyUSB0.*
lrwxrwxrwx 1 root root 11 /dev/ttyUSB0.app1 -> /dev/pts/25
lrwxrwxrwx 1 root root 11 /dev/ttyUSB0.app2 -> /dev/pts/26

# Verify that data is coming through
$ cat /dev/ttyUSB0.app1
�~��3�0���0���������������������^C

$ cat /dev/ttyUSB0.app2
�~��3�0���0���������������������^C

# Configure your other apps that previously used /dev/ttyUSB0 with either
# /dev/ttyUSB0.app1 or /dev/ttyUSB0.app2

TODO

  • Unit testing
  • More platform support
  • Improve data flow control