Persistent Connection in C socket programming

Question

I have written a client code to create a socket and send a request to the client and as HTTP 1.1 uses Connection:Alive by default still the connection closes.How can i create a persistent connection such that the server listens to every request until the connection is closed.The client side code is:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

void error(char *msg){
perror(msg);
exit(0);
}

int main(int argc, char *argv[])
{
 int sockfd, portno, n,i;
int Max_Requests;
struct sockaddr_in serv_addr;
struct hostent *server;

char buffer[256];
if (argc < 3) {
   fprintf(stderr,"usage %s hostname port\n", argv[0]);
   exit(0);
}
Max_Requests=atoi(argv[3]);
portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (sockfd < 0)
    error("ERROR opening socket");

server = gethostbyname(argv[1]);
if (server == NULL) {
    fprintf(stderr,"ERROR, no such host\n");
    exit(0);
}

bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,(char *)&serv_addr.sin_addr.s_addr,server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
    error("ERROR connecting");

i=0;
while(i<Max_Requests){
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);
    n = write(sockfd,buffer,strlen(buffer));
    if (n < 0)
        error("ERROR writing to socket");

    bzero(buffer,256);
    n = read(sockfd,buffer,255);
    if (n < 0)
        error("ERROR reading from socket");

    printf("%s\n",buffer);
    i++;
}
return 0;
}

Answer 1

The problem is your use of fgets to read input from the user to form the request.

The problem with it is how you use it, namely to read a single line that you send to the server as the request. You then promptly go to the read call and wait for the response, without having sent the full request and its headers.

That will lead the server to time-out and close the connection, since it haven't received a full request.