Server terminates exactly after one request is handled - c

Question

I wrote this server program to accept request from one client at a time ,serve the request and then wait for further request ,the outer while loop is supposed to keep running but the program terminates after exactly one request
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<stdio.h>
#include<unistd.h>
#include<string.h>
#include<sys/types.h>
#include<sys/signal.h>
#define SUCCESS 0
#define ERROR 1
#define END_LINE 0x0
#define SERVER_PORT 1306
#define MAX_MSG 100
static int words = 0;
static int letters = 0;
static int delim = 0;
int
main (int argc, char *argv[])
{
int i, serv_sd, cli_sd, cliLen;
struct sockaddr_in cliAddr, servAddr;
char line[MAX_MSG], buffer[MAX_MSG];
serv_sd = socket (AF_INET, SOCK_STREAM, 0);
if (serv_sd < 0)
{
perror ("cannot open socket ");
return ERROR;
}
servAddr.sin_family = AF_INET;
servAddr.sin_addr.s_addr = inet_addr ("127.0.0.1");
/* servAddr.sin_addr.s_addr = htonl(INADDR_ANY); */
servAddr.sin_port = htons (SERVER_PORT);
printf (" Socket Id is %d, Server port is %d\n", serv_sd, SERVER_PORT);
if (bind (serv_sd, (struct sockaddr *) &servAddr, sizeof (servAddr)) < 0)
{
perror ("cannot bind port ");
return ERROR;
}
listen (serv_sd, 5);
while (1)
{
printf ("%s :: waiting for data on port TCP %u\n", argv[0],
SERVER_PORT);
cliLen = sizeof (cliAddr);
cli_sd = accept (serv_sd, (struct sockaddr *) &cliAddr, &cliLen);
if (cli_sd < 0)
{
perror ("cannot accept connection ");
return ERROR;
}
memset (line, 0x0, MAX_MSG);
while (recv(cli_sd, line, MAX_MSG, 0) != -1)
{
printf ("\n %s:: Received from %s: TCP port %d << %s\n", argv[0],
inet_ntoa (cliAddr.sin_addr),
ntohs (cliAddr.sin_port), line);
words++;
int line_size = strlen (line);
for (i = 0; i < line_size; i++)
{
if (isalnum (line[i]) != 0)
letters++;
else
delim++;
}
printf("\nwords: %d, letters: %d\n,",words,letters);
send(cli_sd, &words, 4, 0);
send(cli_sd, &letters, 4, 0);
send(cli_sd, &delim, 4, 0);
memset (line, 0x0, MAX_MSG);
}//receiver
}//while
}
client
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<stdio.h>
#include<unistd.h>
#define MAX 100
int
main (int argc, int *argv[])
{
int sock_desc, rc, i, serv_port, letters, words, delim;
struct sockaddr_in localAddr, servAddr;
if (argc < 4)
{
printf
("usage: %s <server IP> <Server Port> <data1> <data2> ... <dataN>\n",
argv[0]);
exit (1);
}
servAddr.sin_family = AF_INET;
servAddr.sin_addr.s_addr = inet_addr (argv[1]);
serv_port = atoi (argv[2]);
servAddr.sin_port = htons (serv_port);
sock_desc = socket (AF_INET, SOCK_STREAM, 0);
if (sock_desc < 0)
{
perror ("cannot open socket ");
exit (1);
}
rc = connect (sock_desc, (struct sockaddr *) &servAddr, sizeof (servAddr));
if (rc < 0)
{
perror ("cannot connect ");
exit (1);
}
for (i = 3; i < argc; i++)
{
rc = send (sock_desc, argv[i], strlen (argv[i]) + 1, 0);
if (rc < 0)
{
perror ("Connection lost! ");
exit (1);
}
// printf ("\n %s::Data %d Sent--> %s", argv[0], i - 2, argv[i]);
recv(sock_desc, &words, 4, 0);
recv(sock_desc, &letters, 4, 0);
recv(sock_desc, &delim, 4, 0);
}
printf ("\n");
// close(sock_desc);
printf("\n\nThe message you sent had %d letters, %d words and %d delimiter.\n\n",letters,words,delim+words);
return 0;
}

Answer 1

Your server isn't properly checking if the client shutdown. recv will return 0 if the other side closed the connection. As a result, when you try to call send the server processes gets a SIGPIPE signal. Since you don't have a signal handler for that signal, the process exits.
You need to save the return value of recv and check if it's either -1 (for an error) or 0 (for a shutdown). The return value of send should be checked as well. Also, be sure to close the accepted socket when the inner loop exits.
#include <signal.h>
....
int rval;
...
signal(SIGPIPE,SIG_IGN); // ignore SIGPIPE
...
while ((rval=recv(cli_sd, line, MAX_MSG, 0)) != 0)
{
if (rval == -1) {
perror("recv failed");
break;
}
printf ("\n %s:: Received from %s: TCP port %d << %s\n", argv[0],
inet_ntoa (cliAddr.sin_addr),
ntohs (cliAddr.sin_port), line);
words++;
int line_size = strlen (line);
for (i = 0; i < line_size; i++)
{
if (isalnum (line[i]) != 0)
letters++;
else
delim++;
}
printf("\nwords: %d, letters: %d\n,",words,letters);
if (send(cli_sd, &words, 4, 0) == -1) {
perror("send 1 failed");
break;
}
if (send(cli_sd, &letters, 4, 0) == -1) {
perror("send 1 failed");
break;
}
if (send(cli_sd, &delim, 4, 0) == -1) {
perror("send 1 failed");
break;
}
memset (line, 0x0, MAX_MSG);
}//receiver
close(cli_sd);