Pre-built distributed packages of OpenSER doesn't have TLS support enabled by default, which is required for SapienFed operations. So, you must download OpenSER form its distribution site, and compile it.
First of all, the Makefile must be edited, removing the # comment sign to the line
TLS=1, so that TLS support is activated. Then, we must install (in not already present) some components which are required for the compilation process, i.e.
Now, we can give the command
make all, and if everything has gone fine,
make install (as root).