I'm looking for a way to get hold of network stats in C on Linux and MacOSX. Specifically, I need to monitor the number of bytes uploaded and downloaded from each network adapter on the system - I don't need to do packet inspection, or differentiate between protocols, just a 'total bytes' counter which I can poll at intervals would be fine. In Windows I can do this using the iphlpapi.dll library via GetIfTable (to list the network adapters) and GetIfEntry (to read the stats), but I can't find the Linux/OSX equivalents. My knowledge of C is fairly basic so I would appreciate a solution that isn't too involved. Any help would be much appreciated!
The Darwin netstat source code uses sysctl.
Here's some code that prints the number of bytes in and out on OSX:
#import <Foundation/Foundation.h>
#include <sys/sysctl.h>
#include <netinet/in.h>
#include <net/if.h>
#include <net/route.h>
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
int mib[] = {
CTL_NET,
PF_ROUTE,
0,
0,
NET_RT_IFLIST2,
0
};
size_t len;
if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {
fprintf(stderr, "sysctl: %s\n", strerror(errno));
exit(1);
}
char *buf = (char *)malloc(len);
if (sysctl(mib, 6, buf, &len, NULL, 0) < 0) {
fprintf(stderr, "sysctl: %s\n", strerror(errno));
exit(1);
}
char *lim = buf + len;
char *next = NULL;
u_int64_t totalibytes = 0;
u_int64_t totalobytes = 0;
for (next = buf; next < lim; ) {
struct if_msghdr *ifm = (struct if_msghdr *)next;
next += ifm->ifm_msglen;
if (ifm->ifm_type == RTM_IFINFO2) {
struct if_msghdr2 *if2m = (struct if_msghdr2 *)ifm;
totalibytes += if2m->ifm_data.ifi_ibytes;
totalobytes += if2m->ifm_data.ifi_obytes;
}
}
printf("total ibytes %qu\tobytes %qu\n", totalibytes, totalobytes);
[pool drain];
return 0;
}
I can't speak to OSX but on linux take a look at /proc/net/dev.
If you do 'cat /proc/net/dev' you should see statistics including 'bytes' - the total number of bytes of data transmitted or received by the interface. You can read the file within your own program.
EDIT:
I didn't read your whole question. This article should help you get started with /proc and has a section on /proc/net/dev.
Also, to list the interfaces you can call ioctl with the SIOCGIFCONF option. You can Google for a decent code example on how to loop through the returned data. Or you can simply pull it out of the /proc.net/dev data mentioned above, which should be easier.
on Linux:
low level: check /sys/class/net/eth0/statistics/
slightly higher level: ip -s link show eth0
graphical: iftop
interactive: iptraf
Related
I'm working on a embedded linux system (yocto based) and I'm trying to simply get a list of the camera USB video devices (webcams) numbers with the related connected usb port from a C program.
I'm able to get the devices list with vendor ID and connected port doing this:
void usbdevs()
{
libusb_device*** list=NULL;
libusb_context *context = NULL;
ssize_t count;
uint8_t port;
char ncameras=0;
libusb_init(&context);
count = libusb_get_device_list(context,&list);
for(int i=0; i < MAX_NUM_CAMS; i++)
usb_dev_list[i]=0;
for (size_t idx = 0; idx < count; ++idx) {
libusb_device *device = list[idx];
struct libusb_device_descriptor desc = {0};
libusb_get_device_descriptor(device, &desc);
port = libusb_get_port_number(device);
printf("Vendor:Device = %04x:%04x Port: %d\n", desc.idVendor, desc.idProduct,port);
}
libusb_free_device_list(list, count);
libusb_exit(context);
}
What I need now is to know (from the C application) what v4l2 device number is related to the usb camera port, eg. I've got two webcam (same vendor ID) connected which appear as /dev/video0 and /dev/video1 respectively and I can get the connected port for each one using the above code, but, how can I know which ports are connected each one?
I tried to get information from the devices using ioctl calls as it is recommended in this question but when I run the code:
int checkvideodev()
{
int fd;
struct video_capability video_cap;
struct video_window video_win;
struct video_picture video_pic;
if((fd = open("/dev/video0", O_RDONLY)) == -1){
perror("cam_info: Can't open device");
return 1;
}
if(xioctl(fd, VIDIOCGCAP, &video_cap) == -1)
perror("cam_info: Can't get capabilities");
else {
printf("Name:\t\t '%s'\n", video_cap.name);
printf("Minimum size:\t%d x %d\n", video_cap.minwidth, video_cap.minheight);
printf("Maximum size:\t%d x %d\n", video_cap.maxwidth, video_cap.maxheight);
}
if(xioctl(fd, VIDIOCGWIN, &video_win) == -1)
perror("cam_info: Can't get window information");
else
printf("Current size:\t%d x %d\n", video_win.width, video_win.height);
if(xioctl(fd, VIDIOCGPICT, &video_pic) == -1)
perror("cam_info: Can't get picture information");
else
printf("Current depth:\t%d\n", video_pic.depth);
close(fd);
return 0;
}
I've got the next errors:
cam_info: Can't get capabilities: Inappropriate ioctl for device
cam_info: Can't get window information: Inappropriate ioctl for device
cam_info: Can't get picture information: Inappropriate ioctl for device
If I'm checking through command line for instance I can get the capabilities without issues running:
v4l2-ctl --device-/dev/video0 --list-formats-ext
Any ideas how can this be done?
Thanks in advance.
I don't know if this specifically answers your question, but you can get useful information by globbing certain patterns under /dev or /sys, for example this will return the full device path (including PCI bus) of each video device,
#include <glob.h>
#include <unistd.h>
void list_videos() {
int i;
glob_t globbuf;
if (glob("/sys/class/video4linux/video*", 0, NULL, &globbuf) != 0) {
perror("glob");
return;
}
for (i=0; i < globbuf.gl_pathc; i++) {
char buf[256] = {};
if (readlink(globbuf.gl_pathv[i], buf, sizeof(buf)-1) > 0) {
puts(buf);
}
}
}
On one system with 2 cameras this prints,
../../devices/pci0000:00/0000:00:14.0/usb2/2-1/2-1.1/2-1.1:1.0/video4linux/video0
../../devices/pci0000:00/0000:00:14.0/usb2/2-3/2-3:1.0/video4linux/video1
Other interesting glob strings include /dev/v4l/by-id/* and /dev/v4l/by-path/*.
I have weird problem. I try to communicate with ifm AY1020 via modbusTCP using libmodbus from PC.
My code looks as follow:
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <modbus/modbus.h>
int main()
{
modbus_t *ctx;
uint16_t *tab_reg;
int rc;
int i;
ctx = modbus_new_tcp("192.168.1.250", 502);
modbus_set_debug(ctx, TRUE);
tab_reg = (uint16_t *) malloc(5 * sizeof(uint16_t));
memset(tab_reg, 0, 5 * sizeof(uint16_t));
if (modbus_connect(ctx) == -1)
{
fprintf(stderr, "Connection failed: %s\n",modbus_strerror(errno));
modbus_free(ctx);
return -1;
}
rc = modbus_read_registers(ctx, 3002, 2, tab_reg);
if (rc == -1)
{
fprintf(stderr, "%s\n", modbus_strerror(errno));
return -1;
}
for (i=0; i < rc; i++) {
printf("reg[%d]=%d (0x%X)\n", i, tab_reg[i], tab_reg[i]);
}
modbus_close(ctx);
modbus_free(ctx);
}
Thanks to debug I was able to get the frame that is generated in modbus_read_registers function:
[00][01][00][00][00][06][FF][03][0B][BA][00][02]
And I get this
ERROR Gateway path unavailable
Gateway path unavailable
After analysis you can find that device id in that frame is FF, but according to this error PLC expects 1.
Going further if during debugging I force change this value from FF to 01 everything works fine. It looks like it assign wrong ID.
I would be grateful for any help, advice, solution.
Best,
Paweł
Looking at the Man
You should call modbus_set_slave to set a specific destination device.
TCP
The slave number is only required in TCP if the message must reach a device on a serial network. The special value MODBUS_TCP_SLAVE (0xFF) can be used in TCP mode to restore the default value.
Emphasis mine
Your code should be
modbus_set_slave(ctx, 1);
rc = modbus_read_registers(ctx, 3002, 2, tab_reg);
I have multiple slaves on a RS485 bus. I have been using pymodbus so far but I'm not quite happy with it's performance and other issues. So I wanted to to test libmodus and use that instead.
I wrote a minimal program that reads the model number of my slaves
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <modbus.h>
#include <errno.h>
char *bigendian_vec_to_str(uint16_t *vec, size_t vec_size, char *buff, size_t buff_len)
{
memset(buff, 0, sizeof *buff * buff_len);
int i;
for(i = 0; i < vec_size; ++i)
{
uint16_t fl = vec[i] >> 8;
uint16_t sl = vec[i] & 0xff;
if(2*i >= buff_len - 1)
return buff;
if(fl == 0)
return buff;
buff[2 * i] = fl;
if(2*i + 1 >= buff_len - 1)
return buff;
if(sl == 0)
return buff;
buff[2 * i + 1] = sl;
}
return buff;
}
char *get_model_name_of(modbus_t *modbus, int slave, char *buff, size_t buff_len)
{
modbus_flush(modbus);
modbus_set_slave(modbus, slave);
int rc;
uint16_t reg[9];
memset(reg, 0, sizeof reg);
rc = modbus_read_registers(modbus, 0xe, 8, reg);
if (rc == -1) {
fprintf(stderr, "Error %d while reading: %s\n", errno, modbus_strerror(errno));
return NULL;
}
return bigendian_vec_to_str(reg, 8, buff, buff_len);
}
int main(void)
{
modbus_t *modbus = modbus_new_rtu("/dev/ttyUSB0", 9600, 'N', 8, 1);
modbus_rtu_set_serial_mode(modbus, MODBUS_RTU_RS485);
if (modbus_connect(modbus) == -1) {
fprintf(stderr, "Connexion failed: %s\n", modbus_strerror(errno));
modbus_free(modbus);
return -1;
}
char buff[1024];
int i;
for(i = 2; i < 5; ++i)
{
printf("Model of slave %d: %s\n", i, get_model_name_of(modbus, i, buff, sizeof buff));
}
modbus_free(modbus);
return 0;
}
When I ran this code I got
Model of slave 2: LEFS25B-600
Error 110 while reading: Connection timed out
Model of slave 3: (null)
Model of slave 4: LEHF10K2-16
and it seemed strange that the 2nd module was not responding. So I looped get_model_name_of through 2,3,4,2,3,4,2,3,4.... and every second read attempt ended with Error 110 while reading: Connection timed out. After the iine modbus_set_slave(modbus, slave); I added
usleep(0.005 * 1000000);
and then I didn't get timeouts anymore. I read the man pages twice and I didn't find anything warning me about this. I also searched google but none of the "similar" threads I found were of any help.
What is the best way to deal with multiple slaves? Why does adding a sleep of half of milisecond help here? I mean the code on libmodus does
static int _modbus_set_slave(modbus_t *ctx, int slave)
{
/* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */
if (slave >= 0 && slave <= 247) {
ctx->slave = slave;
} else {
errno = EINVAL;
return -1;
}
return 0;
}
is setting an internal value in the context. Are there any time constraints between the change of an internal value in the context and reading/writing to the bus? If so, how long should I wait after a set_slave? Why does libmodbus set the slave id globally instead of having it as a parameter in the read/write method as other libraries (like pymodbus) do?
Or am I using this API just incorrectly?
Thanks
I may be wrong.. but.. as I understand it. The modbus master sends out a request, targeted at a specfic slave number. The intention is to recieve a reply from the targeted slave and then send a request to the next slave and await a reply from second slave. If the requests are sent out without waiting for reply from the first slave.. then there is a possibility to miss the reply from the second slave(or third or whatever number slave) , while the first slave reply is being sent and recieved by the master.
I am not good in C programming.. but I recommend you check this..as I think that may be why you adding a delay seems to help... ( Also.. part of Modbus protocol does require a pause in signal transmission to define start and end of transmission.)
If I am correct , then the use of a delay will only work well if you know the size of data being sent and the time to calculate a response..For other situations a handshake of some kind would be safe.. Such as read a coil.. that indicates whether data is refreshed and ready to be read from the slave as a possible traffic light . to control timing of requests going to other slave and to avoid collision of responses.
Again.. I am not good in C and if I have misinterpreted the program.. please ignore what I have said.. If it helps.. I would be happy hear.
Peter
I have a piece of code written in POSIX compliant C and it doesn't seem to work correctly. The goal is to read from /dev/random, the interface to the Linux/BSD/Darwin kernel's random number generator and output the written byte to a file. I'm not quite sure what I'm overlooking as I'm sure I've covered every ground. Anyway, here it is:
int incinerate(int number, const char * names[]) {
if (number == 0) {
// this shouldn't happen, but if it does, print an error message
fprintf(stderr, "Incinerator: no input files\n");
return 1;
}
// declare some stuff we'll be using
long long lengthOfFile = 0, bytesRead = 0;
int myRandomInteger;
// open the random file block device
int zeroPoint = open("/dev/random", O_RDONLY);
// start looping through and nuking files
for (int i = 1; i < number; i++) {
int filePoint = open(names[i], O_WRONLY);
// get the file size
struct stat st;
stat(names[i], &st);
lengthOfFile = st.st_size;
printf("The size of the file is %llu bytes.\n", lengthOfFile);
while (lengthOfFile != bytesRead) {
read(zeroPoint, &myRandomInteger, sizeof myRandomInteger);
write(filePoint, (const void*) myRandomInteger, sizeof(myRandomInteger));
bytesRead++;
}
close(filePoint);
}
return 0;
}
Any ideas? This is being developed on OS X but I see no reason why it shouldn't also work on Linux or FreeBSD.
If it helps, I've included the following headers:
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
Instead of
write(filePoint, (const void*) myRandomInteger, sizeof(myRandomInteger));
you surely meant to write
write(filePoint, (const void*) &myRandomInteger, sizeof(myRandomInteger));
didn't you? If you use the random bytes read from /dev/random as a pointer, you're almost certain to encounter a segfault sooner or later.
I am New to audio programming.I want to create small application which is capable of playing and gives volume control . I am using alsa-lib.
I want to know what is the purpose of switch (ex.Master Playback switch), enum in mixer elements and what value should i set to those switchs .
Please suggest me some tutorial for mixer settings as well as alsa programming .
Just collecting some here, that have example code:
ALSA Programming HOWTO v.1.0.0 [alsamodular.sourceforge.net]
A tutorial on using the ALSA Audio API [equalarea.com] 2002
A close look at ALSA [volkerschatz.com]
ALSA API - Sample Programs With Source Code By Aquiles Yanez 2005
Introduction to Sound Programming with ALSA | Linux Journal (pg3 with example code) 2004
Note that some of these are old, and API may have changed in the meantime... you can also look up aplay.c (the source for the command line arecord and aplay), but that one is not the easiest to read for starters...
You'll have a tough time finding anything concrete on ALSA, as I have have found from just starting learning it too. The best place to begin is the ALSA project homepage where they link to a number of tutorials, the best one being Dr Nagorni's one IMO.
From what it sounds like you're trying to do, JACK would most likely be a quicker and easier solution, though.
Check out the docs. There are some good examples.
http://www.alsa-project.org/alsa-doc/alsa-lib/examples.html
Be aware of the safe alsa subset.
https://www.winehq.org/pipermail/wine-bugs/2009-June/179698.html
Here's something small I put together using the various sources I could find. It miiiiiiiiiight be a good starting point.
/* Compile with gcc -lasound -pthread threadaudio.c */
#include <alsa/asoundlib.h>
#include <pthread.h>
#include <stdio.h>
unsigned char audiobuffer[0x400];
pthread_mutex_t audiomutex = PTHREAD_MUTEX_INITIALIZER;
void changeaudio (int volume) {
int i;
pthread_mutex_lock(&audiomutex);
for (i = 0; i < sizeof(audiobuffer); i++)
audiobuffer[i] = (random() & 0xff) * volume / 10;
pthread_mutex_unlock(&audiomutex);
}
void *startaudio (void *param)
{
static char *device = "default";
snd_output_t *output = NULL;
int *audiostop = (int*)param;
int err;
snd_pcm_t *handle;
snd_pcm_sframes_t frames;
changeaudio(5);
if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
printf("Playback open error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
if ((err = snd_pcm_set_params(handle,
SND_PCM_FORMAT_U8,
SND_PCM_ACCESS_RW_INTERLEAVED,
1,
48000,
1,
100000)) < 0) { /* 0.1sec */
printf("Playback open error: %s\n", snd_strerror(err));
exit(EXIT_FAILURE);
}
while (!*audiostop) {
err = snd_pcm_wait(handle, 1000);
if (err < 0) {
fprintf (stderr, "poll failed (%d)\n", err);
break;
}
pthread_mutex_lock(&audiomutex);
frames = snd_pcm_writei(handle, audiobuffer, sizeof(audiobuffer));
pthread_mutex_unlock(&audiomutex);
if (frames < 0)
err = snd_pcm_recover(handle, frames, 0);
if (err < 0) {
printf("snd_pcm_writei failed: %s\n", snd_strerror(err));
break;
}
if (frames > 0 && frames < (long)sizeof(audiobuffer))
printf("Short write (expected %li, wrote %li)\n", (long)sizeof(audiobuffer), frames);
}
snd_pcm_close(handle);
}
int main(void)
{
pthread_t audiothread;
int audiostop = 0;
int volume;
pthread_create(&audiothread, NULL, startaudio, &audiostop);
while (1) {
printf("Enter volume 1 through 10. [0 to quit.]: ");
scanf("%d", &volume);
if (volume == 0) break;
changeaudio(volume);
}
audiostop = 1;
pthread_join(audiothread, NULL);
return 0;
}
And after reading the code above you'll probably want to read this article regarding (among other things) not using locks.
http://www.rossbencina.com/code/real-time-audio-programming-101-time-waits-for-nothing