linux - cdc_acm : failed to set dtr/rts - can not communicate with usb cdc device -

i trying enumerate usb cdc device using pic24fj128gb206. device seems enumerated properly.

but when connect device linux pc, getting below warning message kernel.

cdc_acm 1-8.1.6.7:1.0: failed set dtr/rts 

and message repeat when try connect using screen.

screen /dev/ttyacm9 115200 

and not able communicate device pc [ ubuntu, 14.04 ]

when analysing data using wireshark, looks usb communication fine until, host issues urb_control_out , device responds urb status broken pipe (-epipe ) (-32)

can 1 me how debug issue or methods debug further ?