RUI_READ

The RUI_READ verb receives responses, SNA commands, and data into a Windows LUA application's buffer.

The following structure describes the LUA_COMMON member of the VCB used by RUI_READ.

struct LUA_COMMON {
    unsigned short lua_verb;
    unsigned short lua_verb_length;
    unsigned short lua_prim_rc;
    unsigned long  lua_sec_rc;
    unsigned short lua_opcode;
    unsigned long  lua_correlator;
    unsigned char  lua_luname[8];
    unsigned short lua_extension_list_offset;
    unsigned short lua_cobol_offset;
    unsigned long  lua_sid;
    unsigned short lua_max_length;
    unsigned short lua_data_length;
    char FAR *     lua_data_ptr;
    unsigned long  lua_post_handle;
    struct LUA_TH  lua_th;
    struct LUA_RH  lua_rh;
    struct LUA_FLAG1 lua_flag1;
    unsigned char  lua_message_type;
    struct LUA_FLAG2 lua_flag2; 
    unsigned char  lua_resv56[7];
    unsigned char  lua_encr_decr_option;
};

Members

lua_verb

Supplied parameter. Contains the verb code, LUA_VERB_RUI for RUI verbs.

lua_verb_length

Supplied parameter. Specifies the length in bytes of the LUA VCB. It must contain the length of the verb record being issued.

lua_prim_rc

Primary return code set by LUA at the completion of the verb. The valid return codes vary depending on the LUA verb issued.

lua_sec_rc

Secondary return code set by LUA at the completion of the verb. The valid return codes vary depending on the LUA verb issued.

lua_opcode

Supplied parameter. Contains the LUA command code (verb operation code) for the verb to be issued, LUA_OPCODE_RUI_READ.

lua_correlator

Supplied parameter. Contains a user-supplied value that links the verb with other user-supplied information. LUA does not use or change this information. This parameter is optional.

lua_luname

Supplied parameter. Specifies the ASCII name of the local LU used by the Windows LUA session.

RUI_READ only requires this parameter if lua_sid is zero.

This parameter is eight bytes long, padded on the right with spaces (0x20) if the name is shorter than eight characters.

lua_extension_list_offset

Not used by RUI in Microsoft® SNA Server and should be set to zero.

lua_cobol_offset

Not used by LUA in SNA Server and should be zero.

lua_sid

Supplied and returned parameter. Specifies the session identifier and is returned by SLI_OPEN and RUI_INIT. Other verbs use this parameter to identify the session used for the command. If other verbs use the lua_luname parameter to identify sessions, set the lua_sid parameter to zero.

lua_max_length

Specifies the length of received buffer for RUI_READ and SLI_RECEIVE. Not used by other RUI and SLI verbs and should be set to zero.

lua_data_length

Returned parameter. Specifies the length of data returned in lua_peek_data for the RUI_BID verb.

lua_data_ptr

Pointer to the application-supplied buffer that is to receive the data from an RUI_READ verb. Both SNA commands and data are placed in this buffer, and they can be in an EBCDIC format.

When RUI_READ is issued, this parameter points to the location to receive the data from the host.

lua_post_handle

Supplied parameter. Used under Microsoft® Windows NT® and Microsoft® Windows® 95 if asynchronous notification is to be accomplished by events. This variable contains the handle of the event to be signaled or a window handle.

For all other environments, this parameter is reserved and should be set to zero.

lua_th

Returned parameter. Contains the SNA transmission header (TH) of the message sent or received. Various subparameters are set for write functions and returned for read and bid functions. Its subparameters are as follows:

lua_th.flags_fid: Format identification type 2, four bits.
lua_th.flags_mpf: Segmenting mapping field, two bits. Defines the type of data segment. The following values are valid:
0x00Middle segment
0x04Last segment
0x08First segment
0x0COnly segment
lua_th.flags_odai: Originating address field–destination address field (OAF–DAF) assignor indicator, one bit.
lua_th.flags_efi: Expedited flow indicator, one bit.
lua_th.daf: Destination address field (DAF), an unsigned char.
lua_th.oaf: Originating address field (OAF), an unsigned char.
lua_th.snf: Sequence number field, an unsigned char[2].

lua_rh

Returned parameter. Contains the SNA request/response header (RH) of the message sent or received. It is set for the write function and returned by the read and bid functions. Its subparameters are as follows:

lua_rh.rri: Request-response indicator, one bit.
lua_rh.ruc: RU category, two bits. The following values are valid:
LUA_RH_FMD (0x00)FM data segment
LUA_RH_NC (0x20)Network control
LUA_RH_DFC (0x40)Data flow control
LUA_RH_SC (0x60)Session control
lua_rh.fi: Format indicator, one bit.
lua_rh.sdi: Sense data included indicator, one bit.
lua_rh.bci: Begin chain indicator, one bit.
lua_rh.eci: End chain indicator, one bit.
lua_rh.dr1i: Definite response 1 indicator, one bit.
lua_rh.dr2i: Definite response 2 indicator, one bit.
lua_rh.ri: Exception response indicator (for a request), or response type indicator (for a response), one bit.
lua_rh.qri: Queued response indicator, one bit.
lua_rh.pi: Pacing indicator, one bit.
lua_rh.bbi: Begin bracket indicator, one bit.
lua_rh.ebi: End bracket indicator, one bit.
lua_rh.cdi: Change direction indicator, one bit.
lua_rh.csi: Code selection indicator, one bit.
lua_rh.edi: Enciphered data indicator, one bit.
lua_rh.pdi: Padded data indicator, one bit.

lua_flag1

Supplied parameter. Contains a data structure containing flags for messages supplied by the application. Its subparameters are as follows:

lua_flag1.bid_enable: Bid enable indicator, one bit.
lua_flag1.close_abend: Close immediate indicator, one bit.
lua_flag1.nowait: No wait for data flag, one bit.
lua_flag1.sscp_exp: SSCP expedited flow, one bit.
lua_flag1.sscp_norm: SSCP normal flow, one bit.
lua_flag1.lu_exp: LU expedited flow, one bit.
lua_flag1.lu_norm: LU normal flow, one bit.

Set lua_flag1.nowait to 1 to indicate that you want RUI_READ to return immediately whether or not data is available to be read, or set it to zero if you want the verb to wait for data before returning.

Set lua_flag1.bid_enable to 1 to re-enable the most recent RUI_BID (equivalent to issuing RUI_BID again with exactly the same parameters as before), or set it to zero if you do not want to re-enable RUI_BID. Note that re-enabling the previous RUI_BID reuses the VCB originally allocated for it, so this VCB must not have been freed or modified.

Set one or more of the following flags to 1 to indicate from which message flow to read data:

lua_flag1.sscp_exp

lua_flag1.lu_exp

lua_flag1.sscp_norm

lua_flag1.lu_norm

If more than one flag is set, the highest-priority data available is returned. The order of priorities (highest first) is: SSCP expedited, LU expedited, SSCP normal, LU normal. The equivalent flag in the lua_flag2 group is set to indicate from which flow the data was read.

lua_message_type

Specifies the type of the inbound or outbound SNA commands and data. Returned parameter. Specifies the type of SNA message indicated to RUI_READ. Possible values are:

LUA_MESSAGE_TYPE_LU_DATA

LUA_MESSAGE_TYPE_SSCP_DATA

LUA_MESSAGE_TYPE_RQR

LUA_MESSAGE_TYPE_BID

LUA_MESSAGE_TYPE_BIND

LUA_MESSAGE_TYPE_BIS

LUA_MESSAGE_TYPE_CANCEL

LUA_MESSAGE_TYPE_CHASE

LUA_MESSAGE_TYPE_CLEAR

LUA_MESSAGE_TYPE_CRV

LUA_MESSAGE_TYPE_LUSTAT_LU

LUA_MESSAGE_TYPE_LUSTAT_SSCP

LUA_MESSAGE_TYPE_QC

LUA_MESSAGE_TYPE_QEC

LUA_MESSAGE_TYPE_RELQ

LUA_MESSAGE_TYPE_RTR

LUA_MESSAGE_TYPE_SBI

LUA_MESSAGE_TYPE_SHUTD

LUA_MESSAGE_TYPE_SIGNAL

LUA_MESSAGE_TYPE_SDT

LUA_MESSAGE_TYPE_STSN

LUA_MESSAGE_TYPE_UNBIND

LU_DATA, LUSTAT_LU, LUSTAT_SSCP, and SSCP_DATA are not SNA commands.

lua_flag2

Returned parameter. Contains flags for messages returned by LUA. Its subparameters are as follows:

lua_flag2.bid_enable: Indicates that RUI_BID was successfully re-enabled if set to 1.
lua_flag2.async: Indicates that the LUA interface verb completed asynchronously if set to 1.
lua_flag2.sscp_exp: Indicates SSCP expedited flow if set to 1.
lua_flag2.sscp_norm: Indicates SSCP normal flow if set to 1.
lua_flag2.lu_exp: Indicates LU expedited flow if set to 1.
lua_flag2.lu_norm: Indicates LU normal flow if set to 1.

lua_resv56

Reserved and should be set to zero.

lua_encr_decr_option

Reserved and should be set to zero.

Return Codes

LUA_OK

Primary return code; the verb executed successfully.

LUA_DATA_INCOMPLETE: Secondary return code; RUI_READ was not able to return all of the data received because the application's data buffer (indicated by lua_max_length) was not large enough. Subsequent RUI_READ requests can be issued to retrieve the remaining RUI data.
Note that this is not the default behavior for RUI_READ and is only enabled when lua_resv56[3] is set to a nonzero value in the verb control block when calling RUI_INIT during session establishment. See Remarks for more details.

LUA_CANCELED

Primary return code; the verb did not complete successfully because it was canceled by another verb or by an internal error.

LUA_PURGED: Secondary return code; RUI_READ has been canceled by RUI_PURGE.
LUA_TERMINATED: Secondary return code; RUI_TERM was issued while RUI_READ was pending.

LUA_PARAMETER_CHECK

Primary return code; the verb did not execute because of a parameter error.

LUA_BAD_DATA_PTR

Secondary return code; the lua_data_ptr parameter contained an invalid value.

LUA_BAD_SESSION_ID

Secondary return code; an invalid value for lua_sid was specified in the VCB.

LUA_BID_ALREADY_ENABLED

Secondary return code; lua_flag1.bid_enable was set to re-enable RUI_BID but the previous RUI_BID was still in progress.

LUA_DUPLICATE_READ_FLOW

Secondary return code; the flow flags in the lua_flag1 group specified one or more session flows for which RUI_READ was already outstanding. Only one RUI_READ at a time can be waiting on each session flow.

LUA_INVALID_FLOW

Secondary return code; none of the lua_flag1 flow flags was set. At least one of these flags must be set to 1, to indicate from which flow or flows to read.

LUA_INVALID_POST_HANDLE

Secondary return code; for a Windows NT or Windows 95 system using events as the asynchronous posting method, the Windows LUA VCB does not contain a valid event handle.

For a Windows version 3.x system, the Windows LUA VCB does not contain the valid procedure address returned by the MakeProcInstance command.

For OS/2, the Windows LUA VCB does not contain a valid semaphore or queue handle, which is needed when the verb completes asynchronously.

LUA_NO_PREVIOUS_BID_ENABLED

Secondary return code; lua_flag1.bid_enable was set to re-enable RUI_BID, but there was no previous RUI_BID that could be enabled. (See Remarks for more information.)

LUA_RESERVED_FIELD_NOT_ZERO

Secondary return code; a reserved field in the verb record or a parameter not used by this verb was set to a nonzero value.

LUA_VERB_LENGTH_INVALID

Secondary return code; an LUA verb was issued with the value of lua_verb_length unexpected by LUA.

LUA_STATE_CHECK

Primary return code; the verb did not execute because it was issued in an invalid state.

LUA_NO_RUI_SESSION: Secondary return code; RUI_INIT has not yet completed successfully for the LU name specified on RUI_READ.

LUA_NEGATIVE_RSP

Primary return code; indicates one of the following two cases, which can be distinguished by the secondary return code:

LUA detected an error in the data received from the host. Instead of passing the received message to the application on RUI_READ, LUA discards the message (and the rest of the chain if it is in a chain), and sends a negative response to the host. LUA informs the application on a subsequent RUI_READ or RUI_BID that a negative response was sent.
The LUA application previously sent a negative response to a message in the middle of a chain. LUA has purged subsequent messages in this chain, and is now reporting to the application that all messages from the chain have been received and purged.

LUA_SEC_RC: Secondary return code; this parameter is a nonzero secondary return code containing the sense code sent to the host on the negative response. This indicates that LUA detected an error in the host data and sent a negative response to the host. See SNA Considerations for information on interpreting the sense code values that may be returned.
A secondary return code of zero indicates that, following a previous RUI_WRITE of a negative response to a message in the middle of a chain, LUA has now received and discarded all messages from this chain.

LUA_UNSUCCESSFUL

Primary return code; the verb record supplied was valid, but the verb did not complete successfully.

LUA_DATA_TRUNCATED: Secondary return code; the lua_data_length parameter was smaller than the actual length of data received on the message. Only lua_data_length bytes of data were returned to the verb; the remaining data was discarded. Additional parameters are also returned if this secondary return code is obtained.
LUA_NO_DATA: Secondary return code; lua_flag1.nowait was set to indicate immediate return without waiting for data, and no data was currently available on the specified session flow or flows.
LUA_INVALID_PROCESS: Secondary return code; the OS/2 process that issued this verb was not the same process that issued RUI_INIT for this session. Only the process that started a session can issue verbs on that session.

LUA_COMM_SUBSYSTEM_ABENDED

Primary return code; indicates one of the following conditions:

The node used by this conversation encountered an ABEND.
The connection between the TP and the PU 2.1 node was broken (a LAN error).
The SnaBase at the TP's computer encountered an ABEND.

LUA_SESSION_FAILURE

Primary return code; a required SNA Server component has terminated.

LUA_LU_COMPONENT_DISCONNECTED: Secondary return code; indicates that the LUA session failed because of a problem with the link service or with the host LU.
LUA_RUI_LOGIC_ERROR: Secondary return code; an internal error was detected within LUA. This error should not occur during normal operation.

LUA_INVALID_VERB

Primary return code; either the verb code or the operation code, or both, is invalid. The verb did not execute.

LUA_STACK_TOO_SMALL

Primary return code; the stack size of the application is too small to execute the verb. Increase the stack size of your application.

LUA_COMM_SUBSYSTEM_NOT_LOADED

Primary return code; a required component could not be loaded or has terminated while processing the verb. Thus, communication could not take place. Contact the system administrator for corrective action.

LUA_UNEXPECTED_DOS_ERROR

Primary return code; after issuing an operating system call, an unexpected operating system return code was received and is specified in the secondary return code.

Remarks

RUI_INIT must have completed successfully before RUI_READ is issued.

While an existing RUI_READ is pending, you can issue another RUI_READ only if it specifies a different session flow or flows from pending RUI_READ verbs; that is, you cannot have more than one RUI_READ outstanding for the same session flow.

You can specify a particular message flow (LU normal, LU expedited, SSCP normal, or SSCP expedited) from which to read data, or you can specify more than one message flow. You can have multiple RUI_READ verbs outstanding, provided that no two of them specify the same flow.

Data is received by the application on one of four session flows. The four session flows, from highest to lowest priority are:

SSCP expedited
LU expedited
SSCP normal
LU normal

The data flow type that RUI_READ is to process is specified in the lua_flag1 parameter. The application can also specify whether it wants to look at more than one type of data flow. When multiple flow bits are set, the highest priority is received first. When RUI_READ completes processing, lua_flag2 indicates the specific type of flow for which data has been received by the Windows LUA application.

If RUI_BID successfully completes before an RUI_READ is issued, the Windows LUA interface can be instructed to reuse the last RUI_BID verb's VCB. To do this, issue the RUI_READ with lua_flag1.bid_enable set.

The lua_flag1.bid_enable parameter can be used only if the following are true:

RUI_BID has already been issued successfully and has completed.
The storage allocated for RUI_BID has not been freed or modified.
No other RUI_BID is pending.

When using lua_flag1.bid_enable, the RUI_BID storage must not be freed because the last RUI_BID verb's VCB is used. Also, when using lua_flag1.bid_enable, the successful completion of RUI_BID will be posted.

If RUI_READ is issued with lua_flag1.nowait when no data is available to receive, LUA_NO_DATA will be the secondary return code set by the Windows LUA interface.

If the data received is longer than lua_max_length, it is truncated; and only lua_max_length bytes of data are returned. The primary return code LUA_UNSUCCESSFUL and the secondary return code LUA_DATA_TRUNCATED are also returned. The RUI library returns as much data as possible to the application's data buffer, but the remaining data in the RUI is discarded and cannot be extracted on subsequent RUI_READ requests. This forces the RUI application to allocate an RUI_READ data buffer large enough to handle the full RU size.

This default behavior can be changed by setting the value of lua_resv56[3] to a nonzero value in the verb control block when calling RUI_INIT during session establishment. In this case, if the data received is longer than lua_max_length, an RUI_READ request will return a primary return code of LUA_OK and a secondary return code of LUA_DATA_INCOMPLETE. An RUI application can then issue new RUI_READ calls and receive the remainder of the data. Note that this enhancement has not been adopted as part of the Microsoft Windows Open Services Architecture (WOSA) LUA API standard and differs from the implementation of RUI by IBM.

After a message has been read using RUI_READ, it is removed from the incoming message queue and cannot be accessed again. (Note that RUI_BID can be used as a nondestructive read; that is, the application can use it to check the type of data available, but the data remains on the incoming queue and does not need to be used immediately.)

Pacing can be used on the primary-to-secondary half-session (this is specified in the host configuration), to protect the LUA application from being flooded with messages. If the LUA application is slow to read messages, SNA Server delays the sending of pacing responses to the host to slow it down.

RUI_READ

Members

Return Codes

Remarks

See Also