Recv hangs even though I followed all conventions?

Question

I am trying to create a small program that takes a http requests through stdin and sends it to a server. This is the code I am using:

int portno =        3000;
char *message = buf;
char response[4096];
int byte_count;
fsize = strlen(message);
int sockfd;
/* fill in the parameters */
printf("Request:\n%s\n",message);

/* create the socket */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) error("ERROR opening socket");
int sz = (1024 * 1024);
if (setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, &sz, sizeof(sz)) == -1) {
    perror("setsockopt");
    exit(1);
}
struct sockaddr_in saddr;
saddr.sin_family = AF_INET;
saddr.sin_port = htons(portno);
saddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
if (connect(sockfd, &saddr, sizeof(saddr)) == -1) {
    perror("connect");
}
send(sockfd, message, fsize, MSG_NOSIGNAL);
printf("written");
byte_count = recv(sockfd,response,sizeof(response)-1,0); // <-- -1 to leave room for a null terminator
response[byte_count] = 0; // <-- add the null terminator
printf("recv()'d %d bytes of data in buf\n",byte_count);
printf("%s",response);
close(sockfd);

buf is equal to this

GET /alias%2Findex.html HTTP/1.0\r\n
\r\n
\r\n
\r\n

I have done some research through other stack overflow posts and they state that recv usually hangs when the system is waiting for a response. I do not know what could be causing this.

Answer 1

Here is your program only slightly modified. And it works for me. Are you certain whatever server you are running on localhost port 3000 is responding properly? BTW, I had to change the port to 8080 for my system.

#include <netinet/in.h>
#include <netinet/tcp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

char buf[1 << 16] = "GET /file.txt HTTP/1.0\r\n"
                    "\r\n"
                    "\r\n";

int main() {
  int portno = 8080;
  char *message = buf;
  int byte_count;
  int fsize = strlen(message);
  int sockfd;
  /* fill in the parameters */
  printf("Request:\n%s\n", message);

  /* create the socket */
  sockfd = socket(AF_INET, SOCK_STREAM, 0);
  if (sockfd < 0)
    perror("ERROR opening socket");
  int sz = (1024 * 1024);
  if (setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, &sz, sizeof(sz)) == -1) {
    perror("setsockopt");
    exit(1);
  }
  struct sockaddr_in saddr;
  saddr.sin_family = AF_INET;
  saddr.sin_port = htons(portno);
  saddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  if (connect(sockfd, (struct sockaddr *)&saddr, sizeof(saddr)) == -1) {
    perror("connect");
  }
  send(sockfd, message, fsize, MSG_NOSIGNAL);
  printf("written");
  while ((byte_count = recv(sockfd, buf, sizeof(buf) - 1, 0)) >
         0) {            // <-- -1 to leave room for a null terminator
    buf[byte_count] = 0; // <-- add the null terminator
    printf("recv()'d %d bytes of data in buf\n", byte_count);
    printf("%s", buf);
  }
  close(sockfd);

  return 0;
}