C++ socket keeps receiving the same data - c++

Question

I am using this code to receive data from a sensor through sockets. The problem is that I keep receiving the same output for every iteration of the for loop. However I receive a different number for every time I run the code but again, the same number keeps repeating. The sensor should send different every time data but thats not the case here.
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include "port.h"
#define BUFSIZE 2048
int
main(int argc, char **argv)
{
struct sockaddr_in myaddr; /* our address */
struct sockaddr_in remaddr; /* remote address */
socklen_t addrlen = sizeof(remaddr); /* length of addresses */
int recvlen; /* # bytes received */
int fd; /* our socket */
int msgcnt = 0; /* count # of messages we received */
unsigned char buf[BUFSIZE]; /* receive buffer */
/* create a UDP socket */
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror("cannot create socket\n");
return 0;
}
/* bind the socket to any valid IP address and a specific port */
memset((char *)&myaddr, 0, sizeof(myaddr));
myaddr.sin_family = AF_INET;
myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
myaddr.sin_port = htons(SERVICE_PORT);
if (bind(fd, (struct sockaddr *)&myaddr, sizeof(myaddr)) < 0) {
perror("bind failed");
return 0;
}
/* now loop, receiving data and printing what we received */
printf("waiting on port %d\n", SERVICE_PORT);
printf("%s \n \n", "We recieve 10 packets just to confirm the communication");
recvlen = recvfrom(fd, buf, BUFSIZE, 0, (struct sockaddr *)&remaddr, &addrlen);
if (recvlen > 0) {
buf[recvlen] = 0;
printf("received message: \"%u\" (%d bytes)\n", buf, recvlen);
}
else
printf("uh oh - something went wrong!\n");
sprintf(buf, "ack %d", msgcnt++);
printf("sending response \"%u\"\n", buf);
if (sendto(fd, buf, strlen(buf), 0, (struct sockaddr *)&remaddr, addrlen) < 0)
perror("sendto");
int temp = recvlen;
for (;;) {
recvlen = recvfrom(fd, buf, BUFSIZE, 0, (struct sockaddr *)&remaddr, &addrlen);
if (recvlen > 0) {
buf[recvlen] = 0;
printf("received message: \"%u\" (%d bytes)\n", buf, recvlen);
}
}
}
Edit:
Here is the output when i ran the code two seperate times:
trial run and
trial run 2

Answer 1

I believe the problem isn't with your networking code but rather with your printf() calls:
printf("received message: \"%u\" (%d bytes)\n", buf, recvlen);
You are specifying %u to print out the contents of buf, but buf is a char array (not an unsigned integer), so you probably want to be using %s instead.