I'm really confused. I have a C server and it was working great, but then I added some code, and I thought it was working fine until my c program randomly started changing the value of an int to a negative value.
Basically I'm having my server output the total bytes sent and midway through the transmission, always around 2100000000 bytes, the total bytes becomes negative. Here's an example of my output file. The value can't just become negative if you look at my code. So I suspect it's something weirder.
"345000","1470253912","59203","5592","2069901108"
"348000","1470253912","475539","4194","2092449162"
"351000","1470253912","830291","2796","2112043464"
"354000","1470253913","243217","1398","2133985176"
"357000","1470253913","708686","13980","-2135434834"
"360000","1470253914","173646","9786","-2109094024"
"363000","1470253914","514938","6990","-2089413400"
Anyways the thing I added, I commented it out, and I still came across the same error. Just for reference it's commented out in my code under tags "NEW STUFF ADDED". (I added it because of this post: Terminating C program on command line, but make sure writer is finished writing )
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#include <sys/time.h>
int PORT_NUM = 0;
int RecordRate = 3000;
FILE *fp;
typedef struct timeval timeval;
timeval time_;
void error(const char *msg)
{
perror(msg);
exit(1);
}
//NEW STUFF ADDED
//void sig_handler(int signo)
//{
// if (signo == SIGINT) {
// printf("received SIGINT\n");
// exit(0);
// fflush(fp);
// }
//}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[1000000];
struct sockaddr_in serv_addr, cli_addr;
int n;
PORT_NUM = atoi(argv[1]);
fp = fopen(argv[2],"w");
// NEW STUFF ADDED
// if (signal(SIGINT, sig_handler) == SIG_ERR)
// printf("\ncan't catch SIGINT\n");
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
//portno = atoi(argv[1]);
portno = PORT_NUM;
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr,
sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd,10);
clilen = sizeof(cli_addr);
newsockfd = accept(sockfd,
(struct sockaddr *) &cli_addr,
&clilen);
if (newsockfd < 0)
error("ERROR on accept");
int counter = 0;
int total_bytes_sent = 0;
while(1){
bzero(buffer,1000000);
n = read(newsockfd,buffer,999999);
if (n < 0) {
error("ERROR reading from socket");
}
else if (n != 0) {
total_bytes_sent += n;
gettimeofday(&time_, NULL);
if(counter%RecordRate==0){
printf("counter %d \n", counter);
printf("Bytes Sent %d \n", total_bytes_sent);
fprintf(fp,"\"%d\",\"%ld\",\"%d\",\"%d\",\"%d\"\n", counter, time_.tv_sec, time_.tv_usec, n,total_bytes_sent);
}
counter++;
}
}
fclose(fp);
close(newsockfd);
close(sockfd);
return 0;
}
I swear I'm not trolling. I feared it was what I added that did this, but once I commented it out I got the same error. The thing is the error only became present after I added the code. So causation, correlation, no link?
How can this happen? And why always around 2100000000 bytes.
It's not the end of the world. I mean I can just hardcode something that makes sure the value is always, positive but I'm curious as to how this happens. Thanks.
