Socket CAN - Usage

Usage

The application first sets up its access to the CAN interface by initialising a socket (much like in TCP/IP communications), then binding that socket to an interface (or all interfaces, if the application so desires). Once bound, the socket can then be used like a UDP socket via read, write, etc...

Python added support for SocketCan in version 3.3.

There is also a virtual can driver for testing purposes which can be loaded and created in Linux with the commands below.

$ modprobe can $ modprobe can_raw $ modprobe can_bcm $ modprobe vcan $ sudo ip link add dev vcan0 type vcan $ sudo ip link set up vcan0 $ ip link show vcan0 3: vcan0: mtu 16 qdisc noqueue state UNKNOWN link/can

The following code snippet is a working example of the SocketCAN API, that sends a packet using the raw interface. It is based on the notes documented in the Linux Kernel.

#include #include #include #include #include #include #include #include #include #include int main(void) { int s; int nbytes; struct sockaddr_can addr; struct can_frame frame; struct ifreq ifr; char *ifname = "vcan0"; if((s = socket(PF_CAN, SOCK_RAW, CAN_RAW)) < 0) { perror("Error while opening socket"); return -1; } strcpy(ifr.ifr_name, ifname); ioctl(s, SIOCGIFINDEX, &ifr); addr.can_family = AF_CAN; addr.can_ifindex = ifr.ifr_ifindex; printf("%s at index %d\n", ifname, ifr.ifr_ifindex); if(bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("Error in socket bind"); return -2; } frame.can_id = 0x123; frame.can_dlc = 2; frame.data = 0x11; frame.data = 0x22; nbytes = write(s, &frame, sizeof(struct can_frame)); printf("Wrote %d bytes\n", nbytes); return 0; }

The packet can be analyzed on the vcan0 interface using the candump utility which is part of the SocketCAN can-utils package.

can-utils $ ./candump vcan0 vcan0 123 11 22

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