Attention: The old libsml repository is dead!
It still worked but created a compile error on my new and plain Debian Stretch 9.0 box. After opening a bug report I found out about it.
Just pulled the new libsml repository. Compiling works, also modifying sml_server.c works, but you no longer need to modify the line char *device="/dev/ttyUSB0"; with char *device=argv[1]; as it is already in the code.
If you like you can download the already modified sml_server.c file here. I pulled it from the new repository and modified it today.