I have written the following code in the server side for a chat client using C. However, inside the while loop i need to check whether the client has exited the program, that is whether the connection with the client is lost. Please tell me how I can write such a code.
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>
int main()
{
int sock, connected, bytes_recieved , true = 1, pid;
char send_data [1024] , recv_data[1024];
struct sockaddr_in server_addr,client_addr;
int sin_size;
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
{
perror("Socket");
exit(1);
}
if (setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,&true,sizeof(int)) == -1)
{
perror("Setsockopt");
exit(1);
}
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(3128);
server_addr.sin_addr.s_addr = INADDR_ANY;
bzero(&(server_addr.sin_zero),8);
if (bind(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
{
perror("Unable to bind");
exit(1);
}
if (listen(sock, 5) == -1)
{
perror("Listen");
exit(1);
}
printf("\nTCPServer Waiting for client on port 3128");
fflush(stdout);
FILE *log;
log = fopen("time.log", "a");
time_t t;
while(1)
{
sin_size = sizeof(struct sockaddr_in);
connected = accept(sock, (struct sockaddr *)&client_addr,&sin_size);
printf("\n I got a connection from (%s , %d)", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
fflush(stdout);
int pid=fork();
while(1)
{
if(pid == 0)
{
usleep(1000000);
time(&t);
send(connected, ctime(&t),30, 0);
}
else
{
bytes_recieved = recv(connected,recv_data,1024,0);
recv_data[bytes_recieved] = '\0';
fputs(recv_data, log);
fputs("Time: ", log);
time(&t);
fputs(ctime(&t), log);
}
fflush(log);
}
}
fclose(log);
close(sock);
return 0;
}
Please help.
Now I modified the code like this:
while(1)
{
if(pid == 0)
{
usleep(1000000);
time(&t);
send(connected, ctime(&t),30, 0);
}
else
{
bytes_recieved = recv(connected,recv_data,1024,0);
recv_data[bytes_recieved] = '\0';
fputs(recv_data, log);
fputs("Time: ", log);
time(&t);
fputs(ctime(&t), log);
}
fflush(stdout);
fflush(log);
fclose(log);
if(bytes_recieved == 0 || bytes_recieved == -1)
{
close(sock); goto connct;}
}
}
close(sock);
return 0;
On compiling, it goes fine, but on running, it gives the following error output:
*** glibc detected *** ./server: double free or corruption (!prev): 0x09936008 ***
======= Backtrace: =========
/lib/i686/cmov/libc.so.6(+0x6b381)[0xb7659381]
/lib/i686/cmov/libc.so.6(+0x6cbd8)[0xb765abd8]
/lib/i686/cmov/libc.so.6(cfree+0x6d)[0xb765dcbd]
/lib/i686/cmov/libc.so.6(fclose+0x14a)[0xb764982a]
./server[0x8048c21]
/lib/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb7604ca6]
./server[0x8048861]
======= Memory map: ========
08048000-08049000 r-xp 00000000 08:01 133298 /home/harikrishnan/server/server
08049000-0804a000 rw-p 00000000 08:01 133298 /home/harikrishnan/server/server
09936000-09957000 rw-p 00000000 00:00 0 [heap]
b7400000-b7421000 rw-p 00000000 00:00 0
b7421000-b7500000 ---p 00000000 00:00 0
b75bf000-b75dc000 r-xp 00000000 08:01 3653635 /lib/libgcc_s.so.1
b75dc000-b75dd000 rw-p 0001c000 08:01 3653635 /lib/libgcc_s.so.1
b75ed000-b75ee000 rw-p 00000000 00:00 0
b75ee000-b772e000 r-xp 00000000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b772e000-b772f000 ---p 00140000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b772f000-b7731000 r--p 00140000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b7731000-b7732000 rw-p 00142000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b7732000-b7735000 rw-p 00000000 00:00 0
b7744000-b7747000 rw-p 00000000 00:00 0
b7747000-b7748000 r-xp 00000000 00:00 0 [vdso]
b7748000-b7763000 r-xp 00000000 08:01 3654097 /lib/ld-2.11.3.so
b7763000-b7764000 r--p 0001b000 08:01 3654097 /lib/ld-2.11.3.so
b7764000-b7765000 rw-p 0001c000 08:01 3654097 /lib/ld-2.11.3.so
bfd94000-bfda9000 rw-p 00000000 00:00 0 [stack]
*** glibc detected *** ./server: double free or corruption (!prev): 0x09936008 ***
======= Backtrace: =========
/lib/i686/cmov/libc.so.6(+0x6b381)[0xb7659381]
/lib/i686/cmov/libc.so.6(+0x6cbd8)[0xb765abd8]
/lib/i686/cmov/libc.so.6(cfree+0x6d)[0xb765dcbd]
/lib/i686/cmov/libc.so.6(fclose+0x14a)[0xb764982a]
./server[0x8048c21]
/lib/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb7604ca6]
./server[0x8048861]
======= Memory map: ========
08048000-08049000 r-xp 00000000 08:01 133298 /home/harikrishnan/server/server
08049000-0804a000 rw-p 00000000 08:01 133298 /home/harikrishnan/server/server
09936000-09957000 rw-p 00000000 00:00 0 [heap]
b7400000-b7421000 rw-p 00000000 00:00 0
b7421000-b7500000 ---p 00000000 00:00 0
b75bf000-b75dc000 r-xp 00000000 08:01 3653635 /lib/libgcc_s.so.1
b75dc000-b75dd000 rw-p 0001c000 08:01 3653635 /lib/libgcc_s.so.1
b75ed000-b75ee000 rw-p 00000000 00:00 0
b75ee000-b772e000 r-xp 00000000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b772e000-b772f000 ---p 00140000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b772f000-b7731000 r--p 00140000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b7731000-b7732000 rw-p 00142000 08:01 3670051 /lib/i686/cmov/libc-2.11.3.so
b7732000-b7735000 rw-p 00000000 00:00 0
b7744000-b7747000 rw-p 00000000 00:00 0
b7747000-b7748000 r-xp 00000000 00:00 0 [vdso]
b7748000-b7763000 r-xp 00000000 08:01 3654097 /lib/ld-2.11.3.so
b7763000-b7764000 r--p 0001b000 08:01 3654097 /lib/ld-2.11.3.so
b7764000-b7765000 rw-p 0001c000 08:01 3654097 /lib/ld-2.11.3.so
bfd94000-bfda9000 rw-p 00000000 00:00 0 [stack]
Aborted
Any idea what the actual problem is?
if send return SOCKET_ERROR that means that the socket is closed or the connection is lose
so just do