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.

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

Build Dependencies

• C++11 compiler
• cmake
• debhelper
• liblogcpp-dev
• libboost-program-options-dev
• libinicpp-dev

liblogcpp-dev and libinicpp-dev can be found:

# i386 only
deb http://repo.faze.io/ trusty testing

$ sudo apt-get update
$ sudo apt-get install liblogcpp-dev libinicpp-dev

Or you can build them yourself (they are vanilla C++ libraries):

• https://github.com/rkubik/inih
• https://github.com/rkubik/logcpp

Build

1. cmake

In the root of the project.

mkdir build
cd build
cmake ..
make
make install

2. debuild

In the root of the project.

debuild -us -uc -b -j4
debuild clean

Which will produce two debian packages, the runtime daemon and a debugging package.

Configuration

serial-proxy uses a configuration directory of ini files to read serial port configuration. Here is a sample stanza for two physical serial ports:

[/dev/ttyS1]
virtuals = a,b,c
baudrate = 9600
stopbits = 1
bytesize = 8
parity = none
control = none

[/dev/ttyS2]
virtuals = a,b,c
baudrate = 38400

If any of the serial settings are missing from the ini file the defaults below will be used in their place.

baudrate = 9600
stopbits = 1
bytesize = 8
parity = none
control = none

Only one virtual serial port is able to be selected as a writer to communicate with the physical serial port. For the above examples, no virtual serial ports are able to communicate with their upstream master. To enable this feature add a writer = entry to the INI stanza.

[/dev/ttyS1]
virtuals = a,b,c
writer = a
baudrate = 9600
stopbits = 1
bytesize = 8
parity = none
control = none

The above config will read data from /dev/ttyS1 and write the data to a, b, and c. Only a can communicate with the upstream /dev/ttyS1 serial port.

Usage

Run as a daemon:

service serial-proxy restart

Run in foreground and output debug messages to screen:

sproxyd --config /etc/serial-proxy/conf.d --console --loglevel debug

Examples

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

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

# Start serial-proxy
$ service serial-proxy start

# 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

• Add unit tests
• Currently only raw (non-canonical) mode is supported. A configuration field could easily be added to let the user choose canonical vs. non-canonical.

License

MIT