LISTEN
The LISTEN call completes the bind, if BIND has not already been called for the socket, and creates a connection-request queue of a specified length for incoming connection requests.
Restriction: The LISTEN call is not supported for datagram
sockets or raw sockets.
The LISTEN call is used by a server to receive connection requests from clients. When a connection request is received, a new socket is created by a subsequent ACCEPT call, and the original socket continues to listen for additional connection requests. The LISTEN call converts an active socket to a passive socket and conditions it to accept connection requests from clients. Once a socket becomes passive, it cannot initiate connection requests.
Example of LISTEN call
SOC_FUNCTION DC CL16'LISTEN'
S DS H
BACKLOG DS F
ERRNO DS F
RETCODE DS F
CALL DFHSOKET,(SOC_FUNCTION,S,BACKLOG,ERRNO,RETCODE)Input parameters
- SOC_FUNCTION
- A 16-byte character field containing LISTEN. The field is left-justified and padded to the right with blanks.
- S
- A halfword binary number set to the socket descriptor.
- BACKLOG
- A fullword binary number set to the number of communication requests to be queued. Specify a value of 5 for this parameter.
Output parameters
- ERRNO
- A fullword binary field. If RETCODE is negative, the field contains an error number. See Return codes for information about ERRNO return codes.
- RETCODE
- A fullword binary field that returns one of the following:
- Value
- Description
- 0
- Successful call
- -1
- Check ERRNO for an error code