FCNTL

The blocking mode of a socket can either be queried or set to nonblocking using the FNDELAY flag described in the FCNTL call. You can query or set the FNDELAY flag even though it is not defined in your program.

See IOCTL for another way to control a socket’s blocking mode.

Values for commands that are supported by the z/OS® UNIX Systems Services fcntl callable service will also be accepted. See z/OS UNIX System Services Programming: Assembler Callable Services Reference for more information.

Table 1. FCNTL call requirements
Condition	Requirement
Authorization:	Supervisor state or problem state, any PSW key.
Dispatchable unit mode:	Task.
Cross memory mode:	PASN = HASN.
Amode:	31-bit or 24-bit. Note: See the addressability mode (Amode) considerations under CALL instruction API environmental restrictions and programming requirements.
ASC mode:	Primary address space control (ASC) mode.
Interrupt status:	Enabled for interrupts.
Locks:	Unlocked.
Control parameters:	All parameters must be addressable by the caller and in the primary address space.

Figure 1 shows an example of FCNTL call instructions.

Figure 1. FCNTL call instruction example

    WORKING-STORAGE SECTION
        01  SOC-FUNCTION    PIC X(16)  VALUE IS 'FCNTL'.
        01  S               PIC 9(4) BINARY.
        01  COMMAND         PIC 9(8) BINARY.
        01  REQARG          PIC 9(8) BINARY.
        01  ERRNO           PIC 9(8) BINARY.
        01  RETCODE         PIC S9(8) BINARY.
 
 
    PROCEDURE DIVISION
    CALL 'EZASOKET' USING SOC-FUNCTION S COMMAND REQARG
                    ERRNO RETCODE.

For equivalent PL/I and assembly language declarations, see Converting parameter descriptions.