karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm> cec-client --help

cec-client {-h|--help|-l|--list-devices|[COM PORT]}

parameters:
  -h --help                   Shows this help text
  -l --list-devices           List all devices on this system
  -t --type {p|r|t|a}         The device type to use. More than one is possible.
  -p --port {int}             The HDMI port to use as active source.
  -b --base {int}             The logical address of the device to which this 
                              adapter is connected.
  -f --log-file {file}        Writes all libCEC log message to a file
  -r --rom                    Read persisted settings from the EEPROM
  -sf --short-log-file {file} Writes all libCEC log message without timestamps
                              and log levels to a file.
  -d --log-level {level}      Sets the log level. See cectypes.h for values.
  -s --single-command         Execute a single command and exit. Does not power
                              on devices on startup and power them off on exit.
  -o --osd-name {osd name}    Use a custom osd name.
  -m --monitor                Start a monitor-only client.
  -i --info                   Shows information about how libCEC was compiled.
  [COM PORT]                  The com port to connect to. If no COM
                              port is given, the client tries to connect to the
                              first device that is detected.

Type 'h' or 'help' and press enter after starting the client to display all 
available commands
karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm> 

karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm> cec-client --list-devices
libCEC version: 4.0.2,  compiled on request by abuild@buildhost on Linux 4.3.2.1 (x86_64), features: P8_USB, DRM, P8_detect, randr
Found devices: NONE
karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm> 

karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm> cec-client -p
No device type given. Using 'recording device'
CEC Parser created - libCEC version 4.0.2
no serial port given. trying autodetect: FAILED
karl-heinz@linux-c8xv:~/Downloads/epson/iscan-bundle-1.0.4.x64.rpm>