The following code is a socket programming sample for a TCP client.
But when I run this, connect() is returned as Address family not supported by protocol.
I have heard, this problem will happen if the platform does not support ipv6.
But AF_INET I wrote is ipv4.
Also my server, that is CentOS6.4, is configured within an inet6 addr .
Does anyone know why?
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
int
main(){
struct sockaddr_in server;
int sock;
char buf[32];
int n;
sock = socket(AF_INET,SOCK_STREAM,0);
perror("socket");
server.sin_family = AF_INET;
server.sin_port = htons(12345);
inet_pton(AF_INET,"127.0.0.1",&server,sizeof(server));
connect(sock,(struct sockaddr *)&server,sizeof(server));
perror("connect");
memset(buf,0,sizeof(buf));
n = read(sock,buf,sizeof(buf));
perror("read");
printf("%d,%s\n",n,buf);
close(sock);
return 0;
}
The code passes the wrong destination address and wrong number of arguments to inet_pton()
. (For the latter the compiler should have warned you about, btw)
This line
inet_pton(AF_INET, "127.0.0.1", &server, sizeof(server));
should be
inet_pton(AF_INET, "127.0.0.1", &server.sin_addr);
Verbatim from man inet_pton
:
int inet_pton(int af, const char *src, void *dst);
AF_INET
[...] The address is converted to a struct in_addr and copied to dst, which must be sizeof(struct in_addr) (4) bytes (32 bits) long.
Not related to the problem, but also an issue, is that read()
returns ssize_t
not int
.
The following lines shall be adjusted:
int n;
[...]
printf("%d, %s\n", n, buf);
to become:
ssize_t n;
[...]
printf("%zd, %s\n", n, buf);