TCP/IP Programming Manual

Errors
If an error occurs, the return value is set to -1 and the external variable errno is set to one of the
following values:
The specified socket was connected.EISCONN
The specified socket was shut down.ESHUTDOWN
An invalid argument was specified.EINVAL
Usage Guidelines
• This is a nowait call; it must be completed with a call to the AWAITIOX procedure. For a
waited call, use recvfrom.
• The parameters of the recvfrom_nw function are not compatible with those of the recvfrom
function in the 4.3 BSD UNIX operating system.
• The length of the received data is given in the third parameter (count transferred) returned
from the AWAITIOX procedure. This length includes the address information given by
sizeof(sockaddr_in), sizeof (sockaddr_in6), or sizeof(sockaddr_nv) at
the beginning of the buffer.
• For IPv6 use, define the variable r_buffer_ptr as a pointer to a structure of type
sockaddr_in6.
See Nowait Call Errors (page 86) for information on checking errors.
Examples
INET: the following programming example calls the recvfrom_nw function. In this example,
rsock is a socket created by a previous call to socket and fhost is a structure that receives
the address of the host from which the data is received. The data is received in buffer:
#include <socket.h>
#include <in.h>
#include <netdb.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <cextdecs(AWAITIOX, FILE_GETINFO_)>
..
struct sockaddr_in fhost;
int len,rsock;
char buffer [8*1024];
short error, rsock2, rcount;
long tag;
..
error = recvfrom_nw(rsock, buffer, sizeof(buffer), 0,
(struct sockaddr *) &fhost, &len, tag);
if error (!= 0) /* some error checking */
{
printf ("recvfrom_nw failed, error %d\n," errno);
exit (1);
}
rsock2=(short)rsock; /* AWAITIOX/FILE_GETINFO_ expects a short
for socket descriptor */
(void) AWAITIOX (&rsock2,,&rcount,&tag,1l);
(void) FILE_GETINFO_ (rsock2, &error);
if (error != 0)
{
printf ("error from AWAITIOX, error %d\n", errno);
exit (1);
}
recvfrom_nw 163