Io channel conflicts with global/local memory?

Please describe what you mean by "cannot be passed back from kernel to host"? What happens when you write data from kernel to on-board memory and then transfer it to host memory? You are not trying to transfer data from the FPGA external memory to the host in the middle of kernel execution, are you?

Also please elaborate what board you are using and how you are accessing LEDs and I/O. Have you created a custom BSP? I don't know of any OpenCL BSP that supports on-board LEDs. Furthermore, very few manufacturers provide support for network channels in their OpenCL BSP and even that requires a very expensive license for Altera's low-latency MAC core.