VxWorks And The Socket Receive Function

[Bruce Friedman]

VxWorks Gurus -

I hope someone can help as this problem has been driving me crazy for
almost a week now ->

PROBLEM:
I am trying to create a function that will continually examine and read
data from a non-blocking UDP Socket (the non-blocking part is important
here). I can create the socket okay, but I cannot get it to read in a
non-blocking mode. If I use the ioctl() function to set FIONBIO to be non
blocking - it seems to never read anything; just passing over the recvfrom
function like it wasn't there. However - if I put a statement (printf();)
just before or just after the recvfrom statement, it works fine. I have
also been able to successfully get it to block read - waiting until
something is there - but this is no good for me. If I leave out the
ioctl() call, it defaults to blocking. I have also put in an external
delay timer as well as making all variables global. Why oh why does
inserting a printf() work???? Since I can not have a printf() in the final
version of my code, unfortunately this is not an option. I have placed the
code that I am using at the end of this E-Mail in hopes that someone can
find something wrong with it

SYSTEM:
VxWorks version V5.2C
KERNEL: WIND version 2.4
Copyright Wind River Systems, Inc., 1984-1997
CPU: Digital Alpha VME 4/288. Processor #0
Memory Size: 0xd18400.
BSP version V5.2C
DEC Tulip Ethernet Drivers

SAMPLE CODE:
typedef unsigned int in_addr_t;
#include "errno.h"
#include "sys/types.h"
#include "time.h"
#include "vxWorks.h"
#include "fioLib.h" /* printf */
#include "ioLib.h"
#include "stdioLib.h"
#include "taskLib.h"
#include "memLib.h" /* free malloc */
/* #include "varargs.h" */

#include "sys/socket.h" /* bind recvfrom sendto setsockopt shutdown socket */
#include "sys/ioctl.h" /* bind recvfrom sendto setsockopt shutdown socket */
#include "netinet/in.h" /* inet_addr inet_ntoa_b */
#include "socketvar.h" /* bind recvfrom sendto setsockopt shutdown socket */
#include "arpa/inet.h"

#include "inetLib.h" /* inet_addr inet_ntoa_b */
#include "hostLib.h" /* gethostname */
#include "etherLib.h"
#include "ifLib.h"
#include "if_tu.h"
#include "netdb.h"

typedef UINT_32 SOCKET;
#define INVALID_SOCKET (SOCKET)(~0)
#define SOCKET_ERROR (-1)

void main(void)
{
char Recv_Data[4096];
SOCKET The_Socket;
UINT_16 The_Port = 5001;
UINT_16 The_Type = SOCK_DGRAM;
UINT_16 The_Peers_IP = INADDR_ANY;
int Sockaddr_Size = sizeof(struct sockaddr_in);
int Bytes_Rxed = 0;
unsigned long Sock_Opt_ul = 0;
struct sockaddr_in P2P_Rx_Sockaddr_Info;
struct sockaddr_in Rx_Sockaddr_Info;
double Run_Duration_Sec = 100.0;
int Done = 0;
int fionbio = FIONBIO;
int Counter = 0;

/*------------------------------------*/
/* Create the peer to peer Rx socket. */
bzero((char *)&P2P_Rx_Sockaddr_Info, Sockaddr_Size);
P2P_Rx_Sockaddr_Info.sin_family = AF_INET;
P2P_Rx_Sockaddr_Info.sin_addr.s_addr = htonl(The_Peers_IP);
P2P_Rx_Sockaddr_Info.sin_port = htons(The_Port);

The_Socket = socket(AF_INET, SOCK_DGRAM, 0);
ioctl(The_Socket, fionbio, &Sock_Opt_ul);
bind(The_Socket, (struct sockaddr *) &P2P_Rx_Sockaddr_Info, Sockaddr_Size);

printf("\nI'm looking for friends on port %u.\n", The_Port);

/* Messaging loop. */
while (!Done)
{
/* Receive data on this port (non-blocking) and process it. */
Bytes_Rxed = recvfrom(The_Socket, Recv_Data, 4096, 0,
(struct sockaddr *) &Rx_Sockaddr_Info, &Sockaddr_Size);

if (Bytes_Rxed > 0)
printf("I received %d Bytes of Data \n", Bytes_Rxed);

Counter++;
Done = (Counter == 1000);

}

/* Goodbye. */
shutdown(The_Socket, 2);
close (The_Socket);
}

--------------------------------------------------------------------------

_/
_/_/_/_/_/_/ Bruce Friedman | Amherst Systems, Inc
FROM _/_/_/_/ b...@amherst.com | 30 Wilson Rd.
_/_/_/_/_/_/ Voice 716-631-0610 x213 | Buffalo, NY 14221
_/ Fax 716-631-0629 |

[Gordon Uchenick]

Here's what's wrong with your sample code. I have no idea why the =
additional printf would make things work or not work. It seems to me =
that the select() function is much more straightforward. Why don't you =
consider using that?

PROBLEM:
I am trying to create a function that will continually examine and read
data from a non-blocking UDP Socket (the non-blocking part is important
here). I can create the socket okay, but I cannot get it to read in a

non-blocking mode.=20
<SNIP>

void main(void)
{
char Recv_Data[4096];
SOCKET The_Socket;

UINT_16 The_Port =3D 5001;
UINT_16 The_Type =3D SOCK_DGRAM;
UINT_16 The_Peers_IP =3D INADDR_ANY;
int Sockaddr_Size =3D sizeof(struct =
sockaddr_in);
int Bytes_Rxed =3D 0;

HERE'S THE PROBLEM! Sock_Opt_ul should be 1. You are turning OFF =
non-blocking I/O.

unsigned long Sock_Opt_ul =3D 0;

struct sockaddr_in P2P_Rx_Sockaddr_Info;
struct sockaddr_in Rx_Sockaddr_Info;

double Run_Duration_Sec =3D 100.0;
int Done =3D 0;
int fionbio =3D FIONBIO;
int Counter =3D 0;

/*------------------------------------*/
/* Create the peer to peer Rx socket. */
bzero((char *)&P2P_Rx_Sockaddr_Info, Sockaddr_Size);

P2P_Rx_Sockaddr_Info.sin_family =3D AF_INET;
P2P_Rx_Sockaddr_Info.sin_addr.s_addr =3D htonl(The_Peers_IP);
P2P_Rx_Sockaddr_Info.sin_port =3D htons(The_Port);

The_Socket =3D socket(AF_INET, SOCK_DGRAM, 0);
ioctl(The_Socket, fionbio, &Sock_Opt_ul);
bind(The_Socket, (struct sockaddr *) &P2P_Rx_Sockaddr_Info, =
Sockaddr_Size);

printf("\nI'm looking for friends on port %u.\n", The_Port);

/* Messaging loop. */
while (!Done)
{
/* Receive data on this port (non-blocking) and process it. */

YOU SHOULD PUT THIS INTO EACH LOOP ITERATION:

SockAddr_Size =3D sizeof(Rx_Sockaddr_Info);

Bytes_Rxed =3D recvfrom(The_Socket, Recv_Data, 4096, 0,

(struct sockaddr *) &Rx_Sockaddr_Info, &Sockaddr_Size);

if (Bytes_Rxed > 0)
printf("I received %d Bytes of Data \n", Bytes_Rxed);

Counter++;
Done =3D (Counter =3D=3D 1000);

}

<SNIP>