Please follow the blogs given by Jannus Botha.
Please follow this discussion it might help you. The sender channel holds the key.
IDoc Configuration in SAP PO Netweaver 7.4, single stack (AEX)
If error persists after you follow blogs and configure just keep the sender channel in manual mode and give the ECC system's parameters in the channel.
PS-
1-No need to make the JCO RFC Provider
2- checl SMGW
3- No need to give any gateway host and service in SM59 in ECC.
4- Check the Unicode option in SM59 as told.
5- And still if SM58 persists make channel as Manual configuration and give the ECC sysem details.
Things to to do with InboundRA
1- Destination - the destination you created (XI_IDOC_DEFAULT_DESTINATION)
(I hope destination is created correctly with ECC details)
2- MaxThreadCount- 5 or 10
3- Local = true
4- Program id- use same here and sm59
5- in gateway host and service use PI's host and service
Please let us know the results
Thanks and Regards,
Vikas