Re: getsockname behavior (inspecting sin_port)
- From: Michael <mike.lynch@xxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Sat, 13 Dec 2014 09:16:17 -0600
You created an array for Len but didn't initialize it with the length of
sockaddr.
Sent from my Verizon Wireless 4G LTE DROID
Ivan Ribeiro <ivan.ribeiro@xxxxxxxxx> wrote:
>Hi,
>
> Please, I am trying to retrieve which port is listening using the following
>code:
>
>C version:
>
>
>#include <sys/socket.h>
>#include <netinet/in.h>
>#include <stdio.h>
>#include <strings.h>
>
>int main(int argc, char**argv)
>{
> int listenfd;
> struct sockaddr_in servaddr;
>
> listenfd = socket(AF_INET, SOCK_STREAM, 0);
>
> bzero(&servaddr, sizeof(servaddr));
> servaddr.sin_family = AF_INET;
> servaddr.sin_addr.s_addr=htonl(INADDR_ANY);
> servaddr.sin_port=htons(0);
>
> bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
>
> listen(listenfd, 1024);
>
> socklen_t len;
> len = sizeof(servaddr);
> if (getsockname(listenfd, (struct sockaddr *) &servaddr, &len) < 0)
> return (-1);
>
> printf("port: %d\n", ntohs(servaddr.sin_port));
> close (listenfd);
>}
>
>C output:
>[irocha@irrlab servers (master)]$ ./test
>port: 56101
>
>luajit version:
>local ffi = require "ffi"
>
>ffi.cdef[[
>static const int PF_INET = 2;
>static const int AF_INET = PF_INET;
>static const int SOCK_STREAM = 1;
>
>void bzero(void *s, size_t n);
>
>int socket(int domain, int type, int protocol);
>
>typedef uint32_t socklen_t;
>
>static const int SOL_SOCKET = 1;
>static const int SO_REUSEADDR = 2;
>
>typedef unsigned short int sa_family_t;
>typedef uint16_t in_port_t;
>typedef uint32_t in_addr_t;
>
>struct in_addr {
> in_addr_t s_addr;
>};
>
>static const int INADDR_ANY = (in_addr_t)0x00000000;
>
>struct sockaddr {
> sa_family_t sin_family;
> char sa_data[14];
>};
>
>struct sockaddr_in {
> sa_family_t sin_family;
> in_port_t sin_port;
> struct in_addr sin_addr;
>
> unsigned char sin_zero[sizeof(struct sockaddr) -
> sizeof(sa_family_t) -
> sizeof(in_port_t) -
> sizeof(struct in_addr)];
>};
>
>uint16_t htons(uint16_t hostshort);
>uint32_t htonl(uint32_t hostlong);
>uint16_t ntohs(uint16_t netshort);
>
>int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
>
>int listen(int sockfd, int backlog);
>
>int getsockname(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
>
>int close(int fd);
>]]
>
>local C = ffi.C
>
>local listenfd = C.socket(C.AF_INET, C.SOCK_STREAM, 0)
>
>local servaddr = ffi.new("struct sockaddr_in[1]")
>C.bzero(ffi.cast("struct sockaddr *", servaddr), ffi.sizeof(servaddr));
>
>servaddr[0].sin_family = C.AF_INET
>servaddr[0].sin_addr.s_addr=C.htonl(C.INADDR_ANY);
>servaddr[0].sin_port = C.htons(0);
>
>rc = C.bind(listenfd, ffi.cast("struct sockaddr *", servaddr),
>ffi.sizeof(servaddr))
>assert(rc == 0)
>
>rc = C.listen(listenfd, 1024)
>assert(rc == 0)
>
>local len = ffi.new("int32_t[1]")
>rc = C.getsockname(listenfd, ffi.cast("struct sockaddr *", servaddr), len)
>assert(rc == 0)
>
>print(string.format("port: %d\n", C.ntohs(servaddr[0].sin_port)));
>
>rc = C.close(listenfd)
>assert(rc == 0)
>
>luajit output:
>[irocha@irrlab servers (master)]$ luajit test.lua
>port: 0 <<<<<<<<< ALWAYS ZERO!
>
>Why is it not working? Am I missing something?
>
>Best regards,
>
> Ivan Ribeiro Rocha
>
>
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