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HP OpenVMS Systems Documentation |
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HP TCP/IP Services for OpenVMS
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This example sets socket options using the IO$SETMODE function.
TCP/IP Services allows the application to read data after it performs the following operations:
Example 2-15 shows a TCP client using the recv() function to read data.
| Example 2-15 Reading Data (Sockets API) |
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#include <in.h> /* define internet related constants, */
/* functions, and structures */
#include <inet.h> /* define network address info */
#include <netdb.h> /* define network database library info */
#include <socket.h> /* define BSD socket api */
#include <stdio.h> /* define standard i/o functions */
#include <stdlib.h> /* define standard library functions */
#include <string.h> /* define string handling functions */
#define BUFSZ 1024 /* user input buffer size */
#define PORTNUM 12345 /* server port number */
void get_servaddr( void *addrptr )
{
char buf[BUFSIZ];
struct in_addr val;
struct hostent *host;
while ( TRUE )
{
printf( "Enter remote host: " );
if ( fgets(buf, sizeof(buf), stdin) == NULL )
{
printf( "Failed to read user input\n" );
exit( EXIT_FAILURE );
}
buf[strlen(buf)-1] = 0;
val.s_addr = inet_addr( buf );
if ( val.s_addr != INADDR_NONE )
{
memcpy( addrptr, &val, sizeof(struct in_addr) );
break;
}
if ( (host = gethostbyname(buf)) )
{
memcpy( addrptr, host->h_addr, sizeof(struct in_addr) );
break;
}
}
}
int main( void )
{
char buf[512];
int nbytes, sockfd;
struct sockaddr_in addr;
/*
* initialize socket address structure
*/
memset( &addr, 0, sizeof(addr) );
addr.sin_family = AF_INET;
addr.sin_port = htons( PORTNUM );
get_servaddr( &addr.sin_addr );
/*
* create a socket
*/
if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 )
{
perror( "Failed to create socket" );
exit( EXIT_FAILURE );
}
/*
* connect to specified host and port number
*/
printf( "Initiated connection to host: %s, port: %d\n",
inet_ntoa(addr.sin_addr), ntohs(addr.sin_port)
);
if ( connect(sockfd, (struct sockaddr *) &addr, sizeof(addr)) < 0 )
{
perror( "Failed to connect to server" );
exit( EXIT_FAILURE );
}
/*
* read data from connection
*/
nbytes = recv( sockfd,(1) buf,(2) sizeof(buf),(3) 0 (4) );
if ( nbytes < 0 )
{
perror( "Failed to read data from connection" );
exit( EXIT_FAILURE );
}
buf[nbytes] = 0;
printf( "Data received: %s\n", buf );
exit( EXIT_SUCCESS );
}
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This example reads data from a connection using the recv() function.
The $QIO IO$_READVBLK function transfers data received from the internet host (and kept in system dynamic memory) into the address space of the user's process. After the read operation completes, the data in system dynamic memory is discarded.
Example 2-16 shows a TCP client using the IO$_READVBLK function to read data into a single I/O buffer.
| Example 2-16 Reading Data (System Services) |
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#include <descrip.h> /* define OpenVMS descriptors */
#include <efndef.h> /* define 'EFN$C_ENF' event flag */
#include <in.h> /* define internet related constants, */
/* functions, and structures */
#include <inet.h> /* define network address info */
#include <iodef.h> /* define i/o function codes */
#include <netdb.h> /* define network database library info */
#include <ssdef.h> /* define system service status codes */
#include <starlet.h> /* define system service calls */
#include <stdio.h> /* define standard i/o functions */
#include <stdlib.h> /* define standard library functions */
#include <string.h> /* define string handling functions */
#include <stsdef.h> /* define condition value fields */
#include <tcpip$inetdef.h> /* define tcp/ip network constants, */
/* structures, and functions */
#define BUFSZ 1024 /* user input buffer size */
#define PORTNUM 12345 /* server port number */
struct iosb
{ /* i/o status block */
unsigned short status; /* i/o completion status */
unsigned short bytcnt; /* bytes transferred if read/write */
void *details; /* address of buffer or parameter */
};
struct itemlst_2
{ /* item-list 2 descriptor/element */
unsigned short length; /* length */
unsigned short type; /* parameter type */
void *address; /* address of item list */
};
struct sockchar
{ /* socket characteristics */
unsigned short prot; /* protocol */
unsigned char type; /* type */
unsigned char af; /* address format */
};
void get_servaddr( void *addrptr )
{
char buf[BUFSIZ];
struct in_addr val;
struct hostent *host;
while ( TRUE )
{
printf( "Enter remote host: " );
if ( fgets(buf, sizeof(buf), stdin) == NULL )
{
printf( "Failed to read user input\n" );
exit( EXIT_FAILURE );
}
buf[strlen(buf)-1] = 0;
val.s_addr = inet_addr( buf );
if ( val.s_addr != INADDR_NONE )
{
memcpy( addrptr, &val, sizeof(struct in_addr) );
break;
}
if ( (host = gethostbyname(buf)) )
{
memcpy( addrptr, host->h_addr, sizeof(struct in_addr) );
break;
}
}
}
int main( void )
{
char buf[512]; /* data buffer */
int buflen = sizeof( buf ); /* length of data buffer */
struct iosb iosb; /* i/o status block */
unsigned int status; /* system service return status */
unsigned short channel; /* network device i/o channel */
struct sockchar sockchar; /* socket characteristics buffer */
struct sockaddr_in addr; /* socket address structure */
struct itemlst_2 addr_itemlst; /* socket address item-list */
$DESCRIPTOR( inet_device, /* string descriptor with logical */
"TCPIP$DEVICE:" ); /* name of network pseudodevice */
/*
* initialize socket characteristics
*/
sockchar.prot = TCPIP$C_TCP;
sockchar.type = TCPIP$C_STREAM;
sockchar.af = TCPIP$C_AF_INET;
/*
* initialize socket address item-list descriptor
*/
addr_itemlst.length = sizeof( addr );
addr_itemlst.type = TCPIP$C_SOCK_NAME;
addr_itemlst.address = &addr;
/*
* initialize socket address structure
*/
memset( &addr, 0, sizeof(addr) );
addr.sin_family = TCPIP$C_AF_INET;
addr.sin_port = htons( PORTNUM );
get_servaddr( &addr.sin_addr );
/*
* assign i/o channel to network device
*/
status = sys$assign( &inet_device, /* device name */
&channel, /* i/o channel */
0, /* access mode */
0 /* not used */
);
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to assign i/o channel\n" );
exit( status );
}
/*
* create a socket
*/
status = sys$qiow( EFN$C_ENF, /* event flag */
channel, /* i/o channel */
IO$_SETMODE, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
&sockchar, /* p1 - socket characteristics */
0, /* p2 */
0, /* p3 */
0, /* p4 */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to create socket\n" );
exit( status );
}
/*
* connect to specified host and port number
*/
printf( "Initiated connection to host: %s, port: %d\n",
inet_ntoa(addr.sin_addr), ntohs(addr.sin_port)
);
status = sys$qiow( EFN$C_ENF, /* event flag */
channel, /* i/o channel */
IO$_ACCESS, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
0, /* p1 */
0, /* p2 */
&addr_itemlst, /* p3 - remote socket name */
0, /* p4 */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to connect to server\n" );
exit( status );
}
/*
* read data from connection
*/
status = sys$qiow( EFN$C_ENF, /* event flag */
channel, /* i/o channel */
IO$_READVBLK, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
(1) buf, /* p1 - buffer address */
buflen, /* p2 - buffer length */
0, /* p3 */
0, /* p4 */
0, /* p5 */
(2) 0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to read data from connection\n" );
exit( status );
}
buf[iosb.bytcnt] = 0;
printf( "Data received: %s\n", buf );
exit( EXIT_SUCCESS );
}
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This example reads data from a connection using the IO$_READVLK service. The data can be written to a single buffer, as shown here, or a list of buffers.
Before a host can receive (read) IP multicast datagrams destined for a particular multicast group other than all hosts group , the application must direct the host it is running on to become a member of that multicast group.
To join a group or drop membership from a group, specify the following options. Make sure you include the IN.H header file.
struct ip_mreq mreq;
if (setsockopt( sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, & mreq,
sizeof(mreq)) == -1)
perror("setsockopt");
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struct ip_mreq {
struct in_addr (imr_multiaddr); /* IP multicast address of group */
struct in_addr (imr_interface); /* local IP address of interface */
};
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struct ip_mreq mreq;
if (setsockopt( sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq,
sizeof(mreq))== -1)
perror("setsockopt");
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To receive multicast datagrams sent to a specific UDP port, the receiving socket must have been bound to that port using the $QIO(IO$_SETMODE) system service function or the bind() Sockets API function. More than one process can receive UDP datagrams destined for the same port if the function is preceded by a setsockopt() function that specifies the SO_REUSEPORT option. For a complete list of the socket options, see Appendix A.
For example:
int setreuse = 1;
if (setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &setreuse,
sizeof(setreuse)) == -1)
perror("setsockopt");
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When the SO_REUSEPORT option is set, every incoming multicast or broadcast UDP datagram destined for the shared port is delivered to all sockets bound to that port.
Delivery of IP multicast datagrams to SOCK_RAW sockets is determined by
the protocol type of the destination.
2.11 Reading Out-of-Band Data (TCP Protocol)
Only stream-type (TCP/IP) sockets can receive out-of-band (OOB) data. Upon receiving a TCP/IP OOB character, TCP/IP Services stores a pointer in the received stream to the character that precedes the OOB character.
A read operation with a user buffer size larger than the size of the received stream up to the OOB character completes by returning to the user the received stream up to, but not including, the OOB character.
Poll the socket to determine whether additional read operations are
needed before getting all the characters from the stream that precedes
the OOB character.
2.11.1 Reading OOB Data (Sockets API)
You can use the recv() socket function with the MSG_OOB flag set to receive out-of-band data regardless of how many of the preceding characters in the stream you have received.
Example 2-17 shows a TCP server using the recv() function to receive out-of-band data.
| Example 2-17 Reading OOB Data (Sockets API) |
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retval = recv(sock_3,(1) message,(2) sizeof(message), (3)MSG_OOB);(4)
if (retval == -1)
{
perror ("receive");
cleanup( 2, sock_2, sock_3);
}
else
printf (" %s\n", message);
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This example reads data uses the flags argument to the recv() function to specify OOB data.
To receive OOB data from a remote process, use the IO$_READVBLK function with the IO$M_INTERRUPT modifier.
To poll the socket, use a $QIO command with the IO$_SENSEMODE function and the TCPIP$C_IOCTL subfunction that specifies the SIOCATMARK operation.
If the SIOCATMARK returns a value of 0, use additional read QIOs to read more data before reading the OOB character. If the SIOCATMARK returns a value of 1, the next read QIO returns the OOB character.
These functions are useful if a socket has the OOBINLINE socket option set. The OOB character is read with the characters in the stream (IO$_READVBLK) but is not read before the preceding characters. To determine whether or not the first character in the user buffer on the next read is an OOB, poll the socket.
To get a received OOB character for a socket with the socket option OOBINLINE clear, use one of the following functions:
Example 2-18 shows how to use the IO$M_INTERRUPT modifier to read out-of-band data.
| Example 2-18 Reading OOB Data (System Services) |
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/*
** Attempt to receive the OOB data from the client.
** Use the function code of IO$_READVBLK, passing the address of the
** input buffer to P1, and the OOB code, TCPIP$C_MSG_OOB, to P4.
** We support the sending and receiving of a one byte of OOB data.
*/
sysSrvSts = sys$qiow( 0, /* efn.v | 0 */
IOChanClient, /* chan.v */
IO$_READVBLK, /* func.v */
&iosb, /* iosb.r | 0 */
0, 0, /* astadr, astprm: UNUSED */
(1) &OOBBuff, /* p1.r IO buffer */
MaxBuff, /* p2.v IO buffer size */
0, /* p3 UNUSED */
(2) TCPIP$C_MSG_OOB, /* p4.v IO options flag */
0, 0 /* p5, p6 UNUSED */
);
if((( sysSrvSts & 1 ) != 1 ) || /* Validate the system service. */
(( iosb.cond_value & 1 ) != 1)) /* Validate the IO status. */
{
cleanup( IOChanClient );
cleanup( IOChannel );
errorExit( sysSrvSts, iosb.cond_value );
}
else
if( iosb.count == 0 )
printf( " FAILED to receive the message, no connection.\n" );
else
printf( " SUCCEEDED in receiving '%d'\n", OOBBuff );
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This example reads OOB data using the IO$_READVBLK service to specify:
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