The following table lists the ABL elements that are either valid only for working with sockets or have special application in socket programming. The remaining sections explain how to use these elements.

Table 1. ABL for programming sockets
ABL element Description 
BYTES-READ
 An INTEGER attribute on the socket object handle that returns the number of bytes read during the last invocation of the socket READ( ) method. If the last READ( ) method call on the socket failed, this attribute returns 0. 
BYTES-WRITTEN
 An INTEGER attribute on the socket object handle that returns the number of bytes written during the last invocation of the socket WRITE( ) method. If the last WRITE( ) method call on the socket failed, this attribute returns 0. 
CONNECT
 An event received on a server socket object handle that indicates that a socket client is trying to connect. This event, if handled by an input-blocking or PROCESS EVENTS statement, executes any CONNECT event handler defined for the server socket object. You can use this event handler to obtain the handle to the socket object with which the client is communicating. 
CONNECT 
  (connection-parameters )
 A method on the socket object handle that connects a socket handle to a specified TCP/IP port on a specified host. 
CONNECTED( )
 A method on the socket object handle that indicates if a socket handle is currently connected to a port. 
CREATE SERVER-SOCKET
  server-socket-handle
 A statement that creates a server socket object with all attributes set to their default values, and stores its handle in a HANDLE variable. 
CREATE SOCKET socket-handle
 A statement that creates a socket object with all attributes set to their default values and stores its handle in a HANDLE variable. 
DEFINE INPUT PARAMETER
  socket-handle
 A statement that defines the single INPUT parameter to the CONNECT event procedure (specified using the SET-CONNECT-PROCEDURE( ) method). This parameter returns the handle to the socket object created when a socket server receives a CONNECT event, and which the socket server uses to communicate with the corresponding socket client. 
DELETE OBJECT handle
 A statement that you can use to delete a handle, including socket and server socket object handles. To delete a connected socket object, you must first disconnect it using the DISCONNECT( ) method. To delete a server socket object enabled to listen for connections, you must first disable it using the DISABLE-CONNECTIONS( ) method. 
DISABLE-CONNECTIONS( )
 A method on the server socket object handle that indicates that new connections are no longer accepted on the server socket. 
DISCONNECT( )
 A method on the socket object handle that terminates the connection between the socket object and the port to which it is connected. 
ENABLE-CONNECTIONS
  ( connection-parameters )
 A method on the server socket object handle that specifies the TCP/IP port that ABL uses to listen for new connections. Once called, ABL automatically listens for and accepts new connections on the specified port.ENABLE-CONNECTIONS() also lets you specify the length of the pending-connection queue. 
FIRST-SERVER-SOCKET
 A HANDLE attribute on the SESSION object handle that returns the handle to the first entry in the chain of server socket handles for the session. Note that you can have only one server socket object in the list enabled to listen for events at one time. 
FIRST-SOCKET
 A HANDLE attribute on the SESSION object handle that returns the handle to the first entry in the chain of socket handles for the session. 
GET-BYTES-AVAILABLE( )
 A method on the socket object handle that indicates the number of bytes available for reading from the socket. 
GET-SOCKET-OPTION
  ( option-name )
 A method on the socket object handle that returns the specified TCP socket option. ABL supports the following options:
  • TCP-NODELAY
  • SO-LINGER
  • SO-KEEPALIVE
  • SO-REUSEADDR
  • SO-SNDBUF
  • SO-RCVBUF
  • SO-RCVTIMEO
For more information on these options, see ABL Reference and your TCP documentation.		 
LAST-SERVER-SOCKET
 A HANDLE attribute on the SESSION object handle that returns the handle to the last entry in the chain of server socket handles for the session. Note that you can have only one server socket object in the list enabled to listen for events at one time. 
LAST-SOCKET
 A HANDLE attribute on the SESSION object handle that returns the handle to the last entry in the chain of socket handles for the session. 
LOCAL-HOST
 A CHARACTER attribute on the socket object handle that returns the IP address on the local machine where the socket object is connected. 
LOCAL-PORT
 An INTEGER attribute on the socket object handle that returns the local port number of the socket object. 
NEXT-SIBLING
 A HANDLE attribute on the socket and server socket object handle that returns the next entry in the list of socket or server socket handles created for the current OpenEdge session. 
MEMPTR
 The ABL data type used by the socket handle READ( ) and WRITE( ) methods to read and write data on a socket. A MEMPTR expression defines a memory region whose size you must allocate in bytes. MEMPTR functions and statements allow you to read and write data between most other ABL data types and the specified memory region. For more information on the MEMPTR data type, see Introduction to External Program Interfaces. 
PREV-SIBLING
 A HANDLE attribute on the socket and server socket object handle that returns the previous entry in the list of socket or server socket handles created for the current OpenEdge session. 
PROCESS EVENTS
 A statement that you can use to handle any pending CONNECT or READ-RESPONSE events. You can also use any input-blocking statement, such as the WAIT-FOR statement. 
READ(
    memptr-expression 
  , position 
  , bytes-to-read
    [ , mode ] )
 A method on the socket object handle that reads data from the specified socket. The method specifies the MEMPTR memory region and byte position within the region to store the data, a number of bytes to read (and store) from the socket, and a read mode. The read mode indicates if the exact specified number of bytes must be read or up to the specified number of bytes can be read. 
READ-RESPONSE
 An event received on a socket object handle indicating that data is waiting on the socket to be read. This event, if handled by an input-blocking or PROCESS EVENTS statement, executes any READ-RESPONSE event procedure or method defined for the socket object. You can use this event procedure or method if you want to read data from the socket in an event-driven manner.1 
REMOTE-HOST
 A CHARACTER attribute on the socket object handle that returns the IP address of the remote machine with which a connected socket object is communicating. 
REMOTE-PORT
 An INTEGER attribute on the socket object handle that returns the number of the port on the remote machine with which a connected socket object is communicating. 
SELF
 A system handle that returns the handle of the object on which an event is handled in the context of an event procedure. In a CONNECT event procedure, this is the handle to the server socket that is responding to a CONNECT event. In a READ-RESPONSE event procedure, this is the handle to the socket that is responding to a READ-RESPONSE event. 
SENSITIVE
 A LOGICAL attribute on the socket and server socket object handle that indicates whether the object can receive events. Set to TRUE (receive events) by default. 
Server socket object handle
 A handle to a server socket object. This object allows you to listen for and accept TCP/IP connections on a given port. 
SET-CONNECT-PROCEDURE(
  event-internal-procedure
     [ , procedure-context ] )
 A method on the server socket object handle that specifies the name of an internal procedure (CONNECT event procedure) to invoke when a CONNECT event occurs. 
SET-CALLBACK ( 
  "READ-RESPONSE", routine-name [ , routine-context ] )
 A method on the socket object handle that specifies the name of the callback to invoke when a READ-RESPONSE event occurs. 
SET-READ-RESPONSE
-PROCEDURE(
  event-internal-procedure
     [ , procedure-context ] )
 A method on the socket object handle that specifies the name of an internal procedure (READ-RESPONSE event procedure) to invoke when a READ-RESPONSE event occurs.
Socket object handle A handle to a socket object. This object allows you to read or write data on a TCP/IP socket and to perform other TCP/IP socket actions. 
SET-SOCKET-OPTION
  ( name, arguments )
 A method on the socket object handle that sets the specified TCP socket option. ABL supports the following options:
  • TCP-NODELAY
  • SO-LINGER
  • SO-KEEPALIVE
  • SO-REUSEADDR
  • SO-SNDBUF
  • SO-RCVBUF
  • SO-RCVTIMEO
For more information on these options, see ABL Reference and your TCP documentation.		 
SSL-SERVER-NAME
 A CHARACTER attribute on the socket object handle that returns the TLS server's X.500 Subject name field after any TLS session has been established. 
TYPE
 A CHARACTER attribute on the socket and server socket object handle that returns the handle type, which is SERVER-SOCKET for a server socket handle and SOCKET for a socket handle. 
WAIT-FOR ...
 A statement that you can use to handle any pending CONNECT or READ-RESPONSE events. You can also use PROCESS EVENTS or any other input-blocking statement, such as the PROMPT-FOR statement, to handle the events. When a CONNECT or READ-RESPONSE event occurs in the context of these statements, any CONNECT or READ-RESPONSE event procedure specified for the corresponding handle is executed. 
WRITE(
    memptr-expression 
  , position 
  , bytes-to-write )
 A method on the socket object handle that writes data to the specified socket. The method specifies the MEMPTR memory region and byte position within the region from which to write the data, as well as the number of bytes to write from the region.
1 A socket handle receives a READ-RESPONSE event under the same conditions that cause the TCP/IP select function to indicate that a socket is ready to receive results. However, in ABL, you must read data on the socket to continue to receive the event. For more information, see Data detection using the event-driven model.