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// Initially based on https://stackoverflow.com/a/35570418
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
int main(void)
{
int const fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0) {
perror("socket failed");
return 1;
}
struct sockaddr_in const serveraddr = {
.sin_family = AF_INET,
.sin_port = htons(50037u),
.sin_addr.s_addr = htonl(INADDR_ANY),
};
if (bind(fd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0) {
perror("bind failed");
return 1;
}
for (;;) {
struct sockaddr_in source_address;
char buffer[200];
socklen_t source_address_len = sizeof(source_address);
int const length = recvfrom(
fd,
buffer,
sizeof(buffer) - 1,
0,
(struct sockaddr*)&source_address,
&source_address_len);
if (length < 0) {
perror("recvfrom failed");
break;
}
uint32_t const addr = ntohl(source_address.sin_addr.s_addr);
uint8_t const a0 = addr >> 24;
uint8_t const a1 = addr >> 16;
uint8_t const a2 = addr >> 8;
uint8_t const a3 = addr;
printf("%d bytes: '%.*s' from %u.%u.%u.%u:%u\n",
length, (int)length, buffer, a0, a1, a2, a3, source_address.sin_port);
}
close(fd);
}
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