The comments and instructions below are for legacy IP stack in Zephyr. tunslip6 ======== tunslip6 can be used in host side to create a tun device that is connected to a unix socket that qemu is providing. This way it is possible to pass packets between host and target system via slip protocol. You need to connect tunslip6 to the second qemu serial line through a UNIX socket (qemu option -serial unix:/tmp/slip-socket). 1) Start socat $ socat PTY,link=/tmp/slip.dev UNIX-LISTEN:/tmp/slip.sock 2) Start qemu, use the listener demo app. Note that you need to set CONFIG_NETWORKING_UART=y in your configuration. You might need to set the platform and ARCH like this if simple_uart driver is not found in your default platform. $ make PLATFORM_CONFIG=basic_cortex_m3 ARCH=arm \ QEMU_EXTRA_FLAGS="-serial none -serial unix:/tmp/slip.sock" qemu or just simply $ make qemu 3) Start tunslip6 $ sudo ./tunslip6 -s `readlink /tmp/slip.dev` 2001:db8::1/64 4) Send data to listener $ nc -u -6 2001:db8::2 4242 < [ ] $ monitor_15_4 sample.pcap or $ monitor_15_4 sample.pcap /tmp/ip-15-4-1 /tmp/ip-15-4-2 coap-client =========== coap-client is a tool that is run in Linux host side and which connects to coap-server running in qemu. You needs to setup the slip connection (see the steps 1 to 3) in tunslip6 section of this document. Example: $ make coap-client If you want to use DTLS then run client like this $ sudo ./coap-client -i tun0 2001:db8::2 For non-DTLS case, run client like this $ sudo ./coap-client -n -i tun0 2001:db8::2 coap-observe-client =================== You can test the coap-observe-client that is running in qemu using the coap-server example server that is found in libcoap. So get libcoap package which can be found here https://github.com/obgm/libcoap.git Compile and install the libcoap library in host. You needs to setup the slip connection (see the steps 1 to 3) in tunslip6 section of this document. $ /home/user/libcoap/examples/coap-server -A 2001:db8::1 -p 5683 Then in the samples/network/coap_observe_client directory, say $ make qemu