INCL_RFC_IO20 is an ABAP runtime error which you may come across when using or developing within an SAP system. See below for the standard details explaining what it means and how you can avoid or fix this runtime error.
Short Dump Classification: & - Text Include (no Short Dump, only Text Module)
You can view further information about a runtme error by using transaction code ST22 which will show you this and all runtime erros that have happen in your SAP system.
Also check out the Comments section below to view or add related contributions and example screen shots.
RFCIO_ERROR_SAPTEMU_ILLEGAL. Protocol error when communicating with SAPGUI. When communicating with SAPGUI, a protocol error was detected.