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HP OpenVMS systems documentation |
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| Previous | Contents | Index |
To initiate a connection to a TCP server, use the connect() function. Example 2-7 shows a TCP client the connect() function to initiate a connection to a TCP server.
| Example 2-7 Initiating a Connection (Sockets API) |
|---|
#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 )
{
int 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
*/
(1)
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)
);
(2)
if ( connect(sockfd, (struct sockaddr *) &addr, sizeof(addr)) < 0 )
{
perror( "Failed to connect to server" );
exit( EXIT_FAILURE );
}
exit( EXIT_SUCCESS );
}
|
This example shows how to:
To initiate a connection to a TCP server, use the $QIO system service with the IO$_ACCESS service and the p3 argument. The p3 argument of the IO$_ACCESS service is the address of an item_list_2 descriptor that points to the remote socket name.
Example 2-8 shows a TCP client using the IO_$ACCESS service to initiate a connection.
| Example 2-8 Initiating a Connection (System Services) |
|---|
#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 )
{
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$M_SUCCESS) )
{
printf( "Failed to assign i/o channel\n" );
exit( status );
}
/*
* create a socket
*/
(1)
status = sys$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
*/
(2)
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 );
}
exit( EXIT_SUCCESS );
}
|
This example shows how to:
A TCP server program must be able to accept incoming connection requests from client programs. The accept() function:
Example 2-9 shows how to use the accept() function.
| Example 2-9 Accepting a Connection (Sockets API) |
|---|
#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 SERV_BACKLOG 1 /* server backlog */
#define SERV_PORTNUM 12345 /* server port number */
int main( void )
{
int conn_sockfd; /* connection socket descriptor */
int listen_sockfd; /* listen socket descriptor */
unsigned int cli_addrlen; /* returned length of client socket */
/* address structure */
struct sockaddr_in cli_addr; /* client socket address structure */
struct sockaddr_in serv_addr; /* server socket address structure */
/*
* initialize client's socket address structure
*/
memset( &cli_addr, 0, sizeof(cli_addr) );
/*
* initialize server's socket address structure
*/
memset( &serv_addr, 0, sizeof(serv_addr) );
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons( SERV_PORTNUM );
serv_addr.sin_addr.s_addr = INADDR_ANY;
/*
* create a listen socket
*/
if ( (listen_sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0 )
{
perror( "Failed to create socket" );
exit( EXIT_FAILURE );
}
/*
* bind server's ip address and port number to listen socket
*/
if ( bind(listen_sockfd,
(struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0 )
{
perror( "Failed to bind socket" );
exit( EXIT_FAILURE );
}
/*
* set socket as a listen socket
*/
if ( listen(listen_sockfd, SERV_BACKLOG) < 0 )
{
perror( "Failed to set socket passive" );
exit( EXIT_FAILURE );
}
/*
* accept connection from a client
*/
printf( "Waiting for a client connection on port: %d\n",
ntohs(serv_addr.sin_port)
);
cli_addrlen = sizeof(cli_addr);
conn_sockfd = accept( listen_sockfd, (1)
(struct sockaddr *) &cli_addr, (2)
&cli_addrlen (3)
);
if ( conn_sockfd < 0 )
{
perror( "Failed to accept client connection" );
exit( EXIT_FAILURE );
}
printf( "Accepted connection from host: %s, port: %d\n",
inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port)
);
exit( EXIT_SUCCESS );
}
|
In this example of an accept() function:
To accept a connection request:
Specifying the IO$_ACCESS service is mandatory for TCP/IP. The IO$_ACCESS service uses the p4 argument only with the IO$M_ACCEPT modifier. |
Example 2-10 shows a TCP server using the IO$_ACCESS service with the IO$M_ACCEPT modifier to accept incoming connection requests.
| Example 2-10 Accepting a Connection (System Services) |
|---|
#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 SERV_BACKLOG 1 /* server backlog */
#define SERV_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 itemlst_3
{ /* item-list 3 descriptor/element */
unsigned short length; /* length */
unsigned short type; /* parameter type */
void *address; /* address of item list */
unsigned int *retlen; /* address of returned length */
};
struct sockchar
{ /* socket characteristics */
unsigned short prot; /* protocol */
unsigned char type; /* type */
unsigned char af; /* address format */
};
int main( void )
{
struct iosb iosb; /* i/o status block */
unsigned int status; /* system service return status */
unsigned short conn_channel; /* connect inet device i/o channel */
unsigned short listen_channel; /* listen inet device i/o channel */
struct sockchar listen_sockchar; /* listen socket characteristics */
unsigned int cli_addrlen; /* returned length of client socket */
/* address structure */
struct sockaddr_in cli_addr; /* client socket address structure */
struct itemlst_3 cli_itemlst; /* client socket address item-list */
struct sockaddr_in serv_addr; /* server socket address structure */
struct itemlst_2 serv_itemlst; /* server socket address item-list */
$DESCRIPTOR( inet_device, /* string descriptor with logical */
"TCPIP$DEVICE:" ); /* name of network pseudodevice */
/*
* initialize socket characteristics
*/
listen_sockchar.prot = TCPIP$C_TCP;
listen_sockchar.type = TCPIP$C_STREAM;
listen_sockchar.af = TCPIP$C_AF_INET;
/*
* initialize client's item-list descriptor
*/
memset( &cli_itemlst, 0, sizeof(cli_itemlst) );
cli_itemlst.length = sizeof( cli_addr );
cli_itemlst.address = &cli_addr;
cli_itemlst.retlen = &cli_addrlen;
/*
* initialize client's socket address structure
*/
memset( &cli_addr, 0, sizeof(cli_addr) );
/*
* initialize server's item-list descriptor
*/
serv_itemlst.length = sizeof( serv_addr );
serv_itemlst.type = TCPIP$C_SOCK_NAME;
serv_itemlst.address = &serv_addr;
/*
* initialize server's socket address structure
*/
memset( &serv_addr, 0, sizeof(serv_addr) );
serv_addr.sin_family = TCPIP$C_AF_INET;
serv_addr.sin_port = htons( SERV_PORTNUM );
serv_addr.sin_addr.s_addr = TCPIP$C_INADDR_ANY;
/*
* assign i/o channels to network device
*/
status = sys$assign( &inet_device, /* device name */
&listen_channel, /* i/o channel */
0, /* access mode */
0 /* not used */
);
if ( status & STS$M_SUCCESS )
status = sys$assign( &inet_device, /* device name */
&conn_channel, /* i/o channel */
0, /* access mode */
0 /* not used */
);
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to assign i/o channel(s)\n" );
exit( status );
}
/*
* create a listen socket
*/
(1)
status = sys$qiow( EFN$C_ENF, /* event flag */
listen_channel, /* i/o channel */
IO$_SETMODE, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
&listen_sockchar, /* p1 - socket characteristics */
0, /* p2 */
0, /* p3 */
0, /* p4 */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to create socket\n" );
exit( status );
}
/*
* bind server's ip address and port number to listen socket
*/
(2)
status = sys$qiow( EFN$C_ENF, /* event flag */
listen_channel, /* i/o channel */
IO$_SETMODE, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
0, /* p1 */
0, /* p2 */
&serv_itemlst, /* p3 - local socket name */
0, /* p4 */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to bind socket\n" );
exit( status );
}
/*
* set socket as a listen socket
*/
(3)
status = sys$qiow( EFN$C_ENF, /* event flag */
listen_channel, /* i/o channel */
IO$_SETMODE, /* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
0, /* p1 */
0, /* p2 */
0, /* p3 */
SERV_BACKLOG, /* p4 - connection backlog */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to set socket passive\n" );
exit( status );
}
/*
* accept connection from a client
*/
printf( "Waiting for a client connection on port: %d\n",
ntohs(serv_addr.sin_port)
);
(4)
status = sys$qiow( EFN$C_ENF, /* event flag */
listen_channel, /* i/o channel */
IO$_ACCESS|IO$M_ACCEPT,
/* i/o function code */
&iosb, /* i/o status block */
0, /* ast service routine */
0, /* ast parameter */
0, /* p1 */
0, /* p2 */
&cli_itemlst, /* p3 - remote socket name */
&conn_channel, /* p4 - i/o channel for new */
/* connection */
0, /* p5 */
0 /* p6 */
);
if ( status & STS$M_SUCCESS )
status = iosb.status;
if ( !(status & STS$M_SUCCESS) )
{
printf( "Failed to accept client connection\n" );
exit( status );
}
printf( "Accepted connection from host: %s, port: %d\n",
inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port)
);
exit( EXIT_SUCCESS );
}
|
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