# TCP Echo Client Demo for MPS2 Cortex-M3 AN385 emulated using QEMU This FreeRTOS+TCP example demonstrates a TCP Echo Client which sends echo requests to an Echo Server and then receives the echo reply. The Echo Client runs on the MPS2 Cortex-M3 AN385 platform emulated using QEMU. ## Setup Description The demo requires 2 components - 1. Echo Client - The demo in this repository. 1. Echo Server - An external echo server. We need a Virtual Machine (VM) running Linux OS to run this demo. Echo Client runs in the Virtual Machine (VM) and Echo Server runs on the host machine. ``` +--------------------------------------------------------+ | Host Machine | | OS - Any | | Runs - Echo Server | | +--------------------------+ | | | Virtual Machine (VM) | | | | OS - Linux | | | | Runs - Echo Client | | | | | | | +----------------+ | +----------------+ | | | | | | | | | | | | | | | | | | | | Echo Server | <-------> | Echo Client | | | | | | | | | | | | | | | | | | | | | | | | | | | | +----------------+ | +----------------+ | | | | | | | +--------------------------+ | +--------------------------------------------------------+ ``` ## Setting up VM 1. Install a Virtual Machine software on your machine. On Windows you can use [Oracle VirtualBox](https://www.virtualbox.org/) and on Mac you can use [Parallels](https://www.parallels.com/products/desktop/). 2. Launch a Linux VM. We tested using Ubuntu 22.04. 3. Install the following tools in the VM: * [GNU Arm Embedded Toolchain](https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads). * [qemu-arm-system](https://www.qemu.org/download). * Make (Version 4.3): ``` sudo apt install make ``` * ipcalc: ``` sudo apt install ipcalc ``` * brctl: ``` sudo apt install bridge-utils ``` 4. Clone the source code in the VM: ```shell git clone https://github.com/FreeRTOS/FreeRTOS.git --recurse-submodules --depth 1 ``` ## Launch Echo Server Launch Echo Server on the host machine. ### Host OS is Linux * Install `netcat`: ``` sudo apt install netcat ``` * Start an Echo Server on port 7: ```shell sudo nc -l 7 ``` ### Host OS is Windows * Install [Npcap/Nmap](https://nmap.org/download.html#windows). * Start an Echo Server on port 7: ```shell ncat -l 7 ``` ### Host OS is Mac * Install `netcat`: ```shell brew install netcat ``` * Start an Echo Server on port 7: ```shell nc -l -p 7 ``` ## Enable Networking in QEMU The Echo Client in this demo runs in QEMU inside the VM. We need to enable networking in QEMU to enable the Echo Client to be able to reach the Echo Server. Do the following steps in the VM: 1. Run the `ifconfig` command to find the VM's network interface details: ``` enp0s3: flags=4163 mtu 9001 inet 192.168.1.81 netmask 255.255.255.0 broadcast 192.168.15.255 inet6 fe80::89c:55ff:fe3d:18ad prefixlen 64 scopeid 0x20 ether 0a:9c:55:3d:18:ad txqueuelen 1000 (Ethernet) RX packets 15001255 bytes 11443805826 (11.4 GB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 9248218 bytes 2080385000 (2.0 GB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ``` 2. Define a shell variable `VM_NETWORK_INTERFACE` and set its value to the name of the network interface of the VM. For example, in the above output of the `ifconfig` command, name of the the network interface is `enp0s3`: ```shell export VM_NETWORK_INTERFACE=enp0s3 ``` 3. Define a shell variable `VM_IP_ADDRESS` and set its value to the IP address of the VM. For example, in the above output of the `ifconfig` command, IP address of the VM is `192.168.1.81`: ```shell export VM_IP_ADDRESS=192.168.1.81 ``` 4. Define a shell variable `VM_NETMASK` and set its value to the netmask of the VM. For example, in the above output of the `ifconfig` command, netmask of the VM is `255.255.255.0`: ```shell export VM_NETMASK=255.255.255.0 ``` 5. Calculate the CIDR of the VM from the netmask: ```shell $ ipcalc -b 1.1.1.1 $VM_NETMASK | grep Netmask Netmask: 255.255.255.0 = 24 ``` CIDR is `24` in the above output. 6. Define a shell variable `VM_CIDR` and set its value to the CIDR of the VM found in the above step. ```shell export VM_CIDR=24 ``` 7. Find the Default Gateway for the VM: ```shell $ ip route show default via 192.168.1.254 dev enp0s3 proto dhcp src 192.168.1.81 metric 100 ``` Default Gateway is `192.168.1.254` in the above output. 8. Define a shell variable `VM_DEFAULT_GATEWAY` and set its value to the Default Gateway of the VM found in the above step. ```shell export VM_DEFAULT_GATEWAY=192.168.1.254 ``` 9. Find the DNS Server of the VM: ```shell $ grep "nameserver" /etc/resolv.conf nameserver 192.168.1.254 ``` 10. Define a shell variable `VM_DNS_SERVER` and set its value to the DNS Server of the host machine found in the above step. ```shell export VM_DNS_SERVER=192.168.1.254 ``` 11. Pick an IP address for the QEMU which is in the same network as the VM. This IP address must not be in-use by any other machine on the same network. Define a shell variable `QEMU_IP_ADDRESS` and set its value to the picked IP Address. For example, run the following command if you picked `192.168.1.80`: ```shell export QEMU_IP_ADDRESS=192.168.1.80 ``` 12. Pick a MAC address for the QEMU. Define a shell variable `QEMU_MAC_ADDRESS` and set its value to the picked MAC Address. For example, run the following command if you picked `52:54:00:12:34:AD`: ```shell export QEMU_MAC_ADDRESS=52:54:00:12:34:AD ``` 13. Define a shell variable `ECHO_SERVER_IP_ADDRESS` and set its value to the IP address of the Echo Server which is running on the host. For example, run the following command if the IP address of the Echo Server is `192.168.1.204`: ```shell export ECHO_SERVER_IP_ADDRESS=192.168.1.204 ``` 14. Turn off firewall on the VM. On Ubuntu run: ```shell sudo ufw disable sudo ufw status ``` On RedHat/Fedora system run: ```shell sudo systemctl status firewalld sudo systemctl stop firewalld ``` 15. Create virtual bridge (virbr0) and virtual NIC (virbr0-nic) to enable networking in QEMU. ```shell sudo ip link add virbr0 type bridge sudo ip tuntap add dev virbr0-nic mode tap sudo ip addr add $VM_IP_ADDRESS/$VM_CIDR dev virbr0 sudo brctl addif virbr0 $VM_NETWORK_INTERFACE sudo brctl addif virbr0 virbr0-nic sudo ip link set virbr0 up sudo ip link set virbr0-nic up sudo ip route add default via $VM_DEFAULT_GATEWAY dev virbr0 ``` The following diagram shows the setup: ``` +-------------------------------------------------------------------------+ | Virtual Machine (VM) | | | | +-------------------------+ | VM NIC (enp0s3) | | | Virtual NIC (virbr0-nic) +--+ | | QEMU +--+ | | | | | | +--------------+ | | | | | +--------->| virbr0 | ---------->| +--------> Internet | | | | +--------------+ | | | | +--+ Virtual Bridge | | | | | +--+ | +-------------------------+ | | | | | +-------------------------------------------------------------------------+ ``` ## Build and Run Do the following steps in the VM where you cloned the code: 1. Set `configIP_ADDR0`-`configIP_ADDR3` in `FreeRTOSConfig.h` to the value of `QEMU_IP_ADDRESS`: ```shell echo $QEMU_IP_ADDRESS ``` ```c #define configIP_ADDR0 192 #define configIP_ADDR1 168 #define configIP_ADDR2 1 #define configIP_ADDR3 80 ``` 2. Set `configNET_MASK0`-`configNET_MASK3` in `FreeRTOSConfig.h` to the value of `VM_NETMASK`: ```shell echo $VM_NETMASK ``` ```c #define configNET_MASK0 255 #define configNET_MASK1 255 #define configNET_MASK2 255 #define configNET_MASK3 0 ``` 3. Set `configGATEWAY_ADDR0`-`configGATEWAY_ADDR3` in `FreeRTOSConfig.h` to the value of `VM_DEFAULT_GATEWAY`: ```shell echo $VM_DEFAULT_GATEWAY ``` ```c #define configGATEWAY_ADDR0 192 #define configGATEWAY_ADDR1 168 #define configGATEWAY_ADDR2 1 #define configGATEWAY_ADDR3 254 ``` 4. Set `configDNS_SERVER_ADDR0`-`configDNS_SERVER_ADDR3` in `FreeRTOSConfig.h` to the value of `VM_DNS_SERVER`: ```shell echo $VM_DNS_SERVER ``` ```c #define configDNS_SERVER_ADDR0 192 #define configDNS_SERVER_ADDR1 168 #define configDNS_SERVER_ADDR2 1 #define configDNS_SERVER_ADDR3 254 ``` 5. Set `configMAC_ADDR0`-`configMAC_ADDR5` in `FreeRTOSConfig.h` to the value of `QEMU_MAC_ADDRESS`: ```shell echo $QEMU_MAC_ADDRESS ``` ```c #define configMAC_ADDR0 0x52 #define configMAC_ADDR1 0x54 #define configMAC_ADDR2 0x00 #define configMAC_ADDR3 0x12 #define configMAC_ADDR4 0x34 #define configMAC_ADDR5 0xAD ``` 6. Set `configECHO_SERVER_ADDR0`-`configECHO_SERVER_ADDR3` in `FreeRTOSConfig.h` to the value of `ECHO_SERVER_IP_ADDRESS`: ```shell echo $ECHO_SERVER_IP_ADDRESS ``` ```c #define configECHO_SERVER_ADDR0 192 #define configECHO_SERVER_ADDR1 168 #define configECHO_SERVER_ADDR2 1 #define configECHO_SERVER_ADDR3 204 ``` 7. Build: ```shell make ``` 8. Run: ```shell sudo qemu-system-arm -machine mps2-an385 -cpu cortex-m3 \ -kernel ./build/freertos_tcp_mps2_demo.axf \ -netdev tap,id=mynet0,ifname=virbr0-nic,script=no \ -net nic,macaddr=$QEMU_MAC_ADDRESS,model=lan9118,netdev=mynet0 \ -object filter-dump,id=tap_dump,netdev=mynet0,file=/tmp/qemu_tap_dump\ -display gtk -m 16M -nographic -serial stdio \ -monitor null -semihosting -semihosting-config enable=on,target=native ``` 9. You should see that following output on the terminal of the Echo Server (which is running `sudo nc -l 7` or `netcat -l 7` depending on your OS): ``` 0FGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~0123456789:;<=> ? @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~0123456789:;<=>? @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~0123456789:;<=>? @ABCDEFGHIJKLM ``` ## Debug 1. Build with debugging symbols: ``` make DEBUG=1 ``` 2. Start QEMU in the paused state waiting for GDB connection: ```shell sudo qemu-system-arm -machine mps2-an385 -cpu cortex-m3 -s -S \ -kernel ./build/freertos_tcp_mps2_demo.axf \ -netdev tap,id=mynet0,ifname=virbr0-nic,script=no \ -net nic,macaddr=$QEMU_MAC_ADDRESS,model=lan9118,netdev=mynet0 \ -object filter-dump,id=tap_dump,netdev=mynet0,file=/tmp/qemu_tap_dump\ -display gtk -m 16M -nographic -serial stdio \ -monitor null -semihosting -semihosting-config enable=on,target=native ``` 3. Run GDB: ```shell $ arm-none-eabi-gdb -q ./build/freertos_tcp_mps2_demo.axf (gdb) target remote :1234 (gdb) break main (gdb) c ``` 4. The above QEMU command creates a network packet dump in the file `/tmp/qemu_tap_dump` which you can examine using `tcpdump` or WireShark: ```shell sudo tcpdump -r /tmp/qemu_tap_dump | less ```