| FILENAME, SOCKET Access Method |
Allows you to read from or write to a TCP/IP socket
| Valid: |
anywhere
|
| Category: |
Data Access
|
![[1]]( ../common/images/sym01.gif) FILENAME fileref SOCKET 'hostname:
portno
<tcpip-options>;
|
![[2]]( ../common/images/sym02.gif) FILENAME fileref SOCKET ':portno'
SERVER
<tcpip-options>;
|
-
fileref
-
is a valid fileref.
-
SOCKET
-
specifies the access method that enables
you to read from or write to a Transmission Control Protocol/Internet Protocol
(TCP/IP) socket.
-
'hostname:portno'
-
is the name or IP address of the host and
the TCP/IP port number to connect to.
-
':portno'
-
is the port number to create for listening.
-
SERVER
-
sets the TCP/IP socket to be a listening
socket, thereby enabling the system to act as a server that is waiting for
a connection.
-
BLOCKSIZE=blocksize
-
where blocksize
is the size of the socket data buffer in bytes.
-
LRECL=lrecl
-
where lrecl
is the logical record length.
-
RECFM=recfm
-
where recfm
is one of three record formats:
-
RECONN=conn-limit
-
where conn-limit
is the maximum number of connections that the server will accept.
-
TERMSTR='eol-char'
-
where eol-char is
the line delimiter to use when RECFM=V. There are three valid values:
A TCP/IP socket is a communication link between two
applications. The server application creates the socket and waits
for a connection. The client application connects to the socket.
With the SOCKET access method, you can use SAS to communicate with another
application over a socket in either client or server mode. The client and
server applications can reside on the same machine or on different machines
that are connected by a network.
As an example, you can develop an application using
Microsoft Visual Basic that communicates with a SAS session that uses the
TCP/IP sockets. Note that Visual Basic does not provide inherent TCP/IP support.
You can obtain a custom control (VBX) from SAS Institute Technical Support
(free of charge) that allows a Visual Basic application to communicate through
the sockets.
In client mode, a local SAS application can use the
SOCKET access method to communicate with a remote application that acts as
a server (and waits for a connection). Before you can connect to a server,
you must know:
The remote application can be another SAS application,
but it doesn't need to be. When the local SAS application connects to the
remote application through the TCP/IP socket, the two applications can communicate
by reading from and writing to the socket as if it were an external file.
If at any time the remote side of the socket is disconnected, the local side
will also automatically terminate.
When the local SAS application is in server mode, it
remains in a wait state until a remote application connects to it. To use
the SOCKET access method in server mode, you need to know only the port number
that you want the server to listen to for a connection. Typically, servers
use well-known ports to listen for connections.
These port numbers are reserved by the system for specific server applications.
For more information about how well-known ports are defined on your system,
refer to the documentation for your TCP/IP software or ask your system administrator.
If the server application does not use a well-known
port, then the system assigns a port number when it establishes the socket
from the local application. However, because any client application that waits
to connect to the server must know the port number, you should try to use
a well-known port.
While a local SAS server application is waiting for
a connection, the SAS System is in a wait state. Each time a new connection
is established, the EOV= variable in the DATA step is set to 1. Because the
server accepts only one connection at a time, no new connections can be established
until the current connection is closed. The connection closes automatically
when the remote client application disconnects. The SOCKET access method continues
to accept new connections until it reaches the limit set in the RECONN option.
This example shows how two SAS applications can talk
over a TCP/IP socket. The local application is in server mode; the remote
application is the client that connects to the server. This example assumes
that the server host name is hp720.unx.sas.com,
that the well-known port number is 5000, and that the server allows a maximum
of three connections before closing the socket.
Here is the program for the server application:
filename local socket ':5000' server reconn=3;
/*The server is using a reserved */
/*port number of 5000. */
data tcpip;
infile local eov=v;
input x $10;
if v=1 then
do; /* new connection when v=1 */
put 'new connection received';
end;
output;
run;
Here is the program for the remote client application:
filename remote socket 'hp720.unx.sas.com:5000';
data _null_;
file remote;
do i=1 to 10;
put i;
end;
run;
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
