Firebird Wire Protocol

1. Introduction

This document describes the Firebird wire protocol. Most of the information was obtained by studying the Firebird source code and implementing the wire protocol in the Firebird .NET provider and Jaybird (Firebird JDBC driver).

The protocol is described in the form of the message sent by the client and received from the server. The described protocol is Firebird/Interbase protocol version 10. Earlier (Interbase) versions of the protocol are not in scope for this document. Changes in later protocol versions are described in notes below the description of the relevant version 10 message (currently higher versions are only partially described).

This document is not complete. It is advisable to consult the InterBase 6 API Guide for additional information on subjects like parsing the status vector, information request items, and the meaning of operations. You can find this manual under “InterBase 6.0 Manuals” in the Reference Manuals section of the Firebird website.

Unless otherwise indicated, a client request must be flushed to the server for processing. For some operations the flush can be deferred, so it is sent together with a different operation. Versions 11 and higher of the wire protocol explicitly support (or even require) deferring of operations, including deferring the read of the response.

In the protocol descriptions below, we include the names of the fields of the structs used in the Firebird sources; this can make it easier to search for how it’s used in Firebird itself.

2. Responses

The wire protocol has a limited set of responses. Some operations have a specific response, which is described together with the operation. Most operation however use one (or more) of the responses described in this section. The meaning and content depend on the operation that initiated the response.

2.1. Generic response

Int32 — p_operation: Operation code

If operation equals op_response:

Int32 — p_resp_object

Object handle

Although 32-bit, valid handle values are always between 0 and 65535 (0xFFFF), with the “normal” range between 0 and 65000, where 0 either represents the connection itself, or means “no value”.

Int64 — p_resp_blob_id

Object ID

Buffer — p_resp_data

Data (meaning depends on the operation).

Byte[] — p_resp_status_vector

Status vector

The format of the status vector is basically <tag><value>[{tag><value>} ...]<end>, with <tag> an Int32, and where parsing of <value> depends on <tag>; <end> is Int32 isc_arg_end — 0. The length can only be determined by correctly parsing the status vector. The first 8 bytes are always an Int32 tag (isc_arg_gds or isc_arg_warning) and an Int32 value.

If the status vector starts with Int32 isc_arg_gds — 1 and the second Int32 is non-zero, it is a failure response.
If it starts with Int32 isc_arg_warning — 18 and the second Int32 is non-zero, it is a success response with warning(s).
Otherwise, if the second Int32 is zero, it is a success response

Information about parsing the status vector can be found in the Interbase 6 API Guide in the documentation set. It might also be advantageous to look at the sources of Firebird .NET Data Provider or Jaybird.

2.2. SQL response

Success response to op_execute2 (see Execute) or op_executeimmediate2 (not yet documented).

Int32 — p_operation: Operation code

If operation equals op_sql_response:

Int32 — p_sqldata_messages: Count of rows following response (in practice, only 1 or 0)
Row data: The row data is not in a buffer like described in Data types, but as a sequence (0..1) of data rows with a special format, see Reading row data.

You can also consider the row data not a part of the SQL response, but something that is sent after the SQL response.

2.3. Fetch response

Success response to op_fetch (see Fetch) and op_fetch_scroll (not yet documented).

Int32 — p_operation: Operation code

If operation equals op_fetch_response:

Int32 — p_sqldata_status

Status

0 — success
100 — end of cursor

Int32 — p_sqldata_messages

Count of rows following response (in practice, only 1 or 0)

A value of 0 indicates end-of-batch (fetch complete). Together with status 100, it also means end-of-cursor, otherwise there are more rows available for a next fetch.

Row data

The row data is not in a buffer like described in Data types, but as a sequence (0..1) of data rows with a special format, see Reading row data.

You can also consider the row data not a part of the fetch response, but something that is sent after the fetch response.

The success response to Fetch is not a single of op_fetch_response, but a sequence of op_fetch_response and row data. That is:

<op-fetch-response (status = 0, count = 1)>
<row-data>
<op-fetch-response (status = 0, count = 1)>
<row-data>
...
if end-of-cursor:
  <op-fetch-response (status = 100, count = 0)>
else:
  <op-fetch-response (status = 0, count = 0)>

Firebird may return fewer rows than requested in Fetch.

2.4. Slice response

Success response to Get slice.

This documentation might not reflect actual encoding in the protocol.

Response to Get slice.

Int32 — p_operation: Operation code

If operation equals op_slice:

Int32 — p_slr_length: Slice length
Int32: Slice length (possibly a buffer?, needs verification)
Buffer: Slice data

3. Databases

3.1. Attach

Attachments to a database are done in two steps, first identification (connect) to the server, then attach to a database.

3.1.1. Identification

The identification and attach handshake changed significantly in protocol 13 (Firebird 3.0), and is not yet documented.

Performs the initial handshake and protocol selection.

Client

Int32 — p_operation

Operation code (op_connect)

Int32 — p_cnct_operation

Operation code; unused in practice, can always be 0. Some implementations use op_attach (19) for historic(?) reasons.

Int32 — p_cnct_cversion

Connect version:

`CONNECT_VERSION2` — `2`	user identification encoding is undefined (Firebird 1.0 — Firebird 2.5)
`CONNECT_VERSION3` — `3`	user identification is UTF-8 encoded (since Firebird 3.0 and higher, but backwards compatible as the version wasn’t checked before Firebird 3.0)

Int32 — p_cnct_client

Architecture type (e.g. arch_generic = 1).

String — p_cnct_file

Database path or alias

The encoding of this is undefined, which can lead to problems with non-ASCII paths if the server and client use a different encoding.

Int32 — p_cnct_count

Count of protocol versions understood (e.g. 1).

Buffer — p_cnct_user_id

User identification

TODO: Needs further description

The next block of data declares the protocol(s) that the client is willing or able to support. It should be sent as many times as protocols are supported (and specified in p_cnct_count above). Values depend on the protocol.

If a client sends more than 10 (Firebird 5.0 and older) or 11 (Firebird 6.0) protocols, the surplus are ignored.

Int32 — p_cnct_version

Protocol version (PROTOCOL_VERSION10)

Int32 — p_cnct_architecture

Architecture type (e.g. arch_generic = 1)

It is possible to use a different architecture value, but then connection is only possible with a server of the same architecture. In addition, it changes how responses and/or data needs to be parsed or encoded (the authors don’t know the exact details). In short, use arch_generic.

Int32 — p_cnct_min_type

Minimum type (e.g. ptype_batch_send = 3)

Possible values:

`ptype_page` — `1`	Page server protocol (never supported in Firebird)
`ptype_rpc` — `2`	Simple remote procedure call (not supported since Firebird 3.0)
`ptype_batch_send` — `3`	Batch sends, no asynchrony
`ptype_out_of_band` — `4`	Batch sends w/ out of band notification (semantics not documented in this manual)
`ptype_lazy_send` — `5`	Deferred packets delivery

Int32 — p_cnct_max_type

Maximum type (e.g. ptype_lazy_send — 5)

If the client wants to set up wire compression, this ptype-code must be OR’ed with pflag_compress (0x100). See also discussion below for server response.

Int32 — p_cnct_weight

Preference weight (e.g. 2). Higher values have higher preference. For equal weights, the last supported occurrence will be selected.

Server

Success response:

Int32 — p_operation: Operation code

If operation equals op_accept:

Int32 — p_acpt_version

Protocol version number accepted by server

Int32 — p_acpt_architecture

Architecture for protocol

Int32 — p_acpt_type

Accepted type and additional flags. Obtain the type by masking with 0xFF.

Known flags:

`pflag_compress` — `0x100`	Turn on compression In the request from client to server, it signals a request to use wire compression. In the response from the server to client, it is an acknowledgement, and wire compression must be enabled after processing this response.
`pflag_win_sspi_nego` — `0x200`	Win_SSPI supports Negotiate security package Only sent from server to client.

Failure response: Generic response

3.1.2. Attachment

Attaches to a database. Attach is the same as Create (op_create), but using op_attach instead of op_create.

Client

Int32 — p_operation

Operation code (op_attach)

Int32 — p_atch_database

Database object id; unused in practice, can always be 0.

String — p_atch_file

Database path or alias

If isc_dpb_utf8_filename is present in the database parameter buffer below, the encoding is UTF-8; otherwise, the encoding is undefined. The isc_dpb_utf8_filename item is supported since Firebird 2.5.

Buffer — p_atch_dpb

Database parameter buffer

Table 1. Example of parameters sent in the DPB
Parameter	Description	Value	Optional
`isc_dpb_version1`	Version (must be first item!)
`isc_dpb_dummy_packet_interval`	Dummy packet interval	120	*
`isc_dpb_sql_dialect`	SQL dialect	3
`isc_dpb_lc_ctype`	Character set	UTF8
`isc_dpb_sql_role_name`	User role	RDB$ADMIN	*
`isc_dpb_connect_timeout`	Connection timeout	10	*
`isc_dpb_user_name`	User name	SYSDBA
`isc_dpb_password`	User password	masterkey

Server

Generic response

3.2. Detach

Detaches from the database. After detach the connection is still open, to disconnect use Disconnect (op_disconnect).

Client

Int32 — p_operation: Operation code (op_detach)
Int32 — p_rlse_object: Database handle (always 0)

Server

Generic response

3.3. Create

Create a database. Create is the same as Attachment (op_attach), but using op_create instead of op_attach.

Client

Int32 — p_operation: Operation code (op_create)
Int32 — p_atch_database: Database object id; unused in practice, can always be 0.
String — p_atch_file: Database path or alias

If isc_dpb_utf8_filename is present in the database parameter buffer below, the encoding is UTF-8; otherwise, the encoding is undefined. The isc_dpb_utf8_filename item is supported since Firebird 2.5.

There are a number of DPB items to configure the newly created database, including page size (isc_dpb_page_size) — which cannot be modified after creation.
Buffer — p_atch_dpb: Database parameter buffer

Server

Generic response

The `CREATE DATABASE` statement

Although Firebird has a CREATE DATABASE statement, the documented syntax is not fully supported by Firebird server. Part of the syntax (e.g. database name, user, password, page size) are parsed by fbclient to execute the op_create (or equivalent for embedded).

After the database is successfully created, fbclient then uses execute immediate (op_execute_immediate) without transaction to execute a reduced CREATE DATABASE statement for additional configuration of the database.

3.4. Drop

Drops the currently attached database.

Client

Int32 — p_operation: Operation code (op_drop_database)
Int32 — p_rlse_object: Database handle

Server

Generic response

3.5. Database information request

Requests database or server information.

Client

Int32 — p_operation: Operation code (op_info_database)
Int32 — p_info_object: Database handle; unused in practice, can always be 0.
Int32 — p_info_incarnation: Incarnation of object (0)

TODO: Usage and meaning?
Buffer — p_info_items: Requested information items

Values of enum db_info_types in Firebird’s inf_pub.h.
Int32 — p_info_buffer_length: Length of buffer available for receiving response

Too small may lead to receiving a truncated buffer, which necessitates requesting information again with a larger size.

The buffer in the response is sized to the actual length of the response (upto the declared available length), so specifying a larger than necessary size does not inflate the response on the wire.

Server

Generic response — on success, p_resp_data holds the requested information.

+ A truncated response is considered a success, and can only be determined by parsing p_resp_data.

3.6. Disconnect

Client

Int32 — p_operation: Operation code (op_disconnect)

No response, remote socket close.

Closing the connection (socket) without sending an op_disconnect will result in “Connection reset by peer” (error 10054 (Windows) or 104 (Linux)) in firebird.log.

4. Transactions

4.1. Start transaction

Starts a transaction with the transaction options specified in the transaction parameter buffer.

Client

Int32 — p_operation: Operation code (op_transaction)
Int32 — p_sttr_database: Database handle; unused in practice, can always be 0.
Buffer — p_sttr_tpb: Transaction parameter buffer

Server

Generic response — on success, p_resp_object is the new transaction handle.

The `SET TRANSACTION` statement

Instead of using op_transaction to start a transaction, it is also possible to use the SET TRANSACTION statement.

This statement needs to be executed with execute immediate (op_execute_immediate) without transaction. On success, the p_resp_object holds the transaction handle.

4.2. Commit transaction

Commits an active or prepared transaction.

Client

Int32 — p_operation: Operation code (op_commit)
Int32 — p_rlse_object: Transaction handle

Server

Generic response

4.3. Rollback transaction

Rolls back an active or prepared transaction.

Client

Int32 — p_operation: Operation code (op_rollback)
Int32 — p_rlse_object: Transaction handle

Server

Generic response

4.4. Commit retaining

Commits an active or prepared transaction, retaining the transaction context.

Client

Int32 — p_operation: Operation code (op_commit_retaining)
Int32 — p_rlse_object: Transaction handle

Server

Generic response

4.5. Rollback retaining

Rolls back an active or prepared transaction, retaining the transaction context.

Client

Int32 — p_operation: Operation code (op_rollback_retaining)
Int32 — p_rlse_object: Transaction handle

Server

Generic response

4.6. Prepare

Performs the first stage of a two-phase commit. After prepare, a transaction is in-limbo until committed or rolled back.

4.6.1. Simple prepare

Client

Int32 — p_operation: Operation code (op_prepare)
Int32 — p_rlse_object: Transaction handle

Server

Generic response

4.6.2. Prepare with message

Associates a message (byte data) with the prepared transaction. This information is stored in RDB$TRANSACTIONS and can be used for recovery purposes.

Client

Int32 — p_operation: Operation code (op_prepare2)
Int32 — p_prep_transaction: Transaction handle
Buffer — p_prep_data: Recovery information

Server

Generic response

4.7. Transaction information request

This is similar to Database information request.

Client

Int32 — p_operation: Operation code (op_info_transaction)
Int32 — p_info_object: Transaction handle
Int32 — p_info_incarnation: Incarnation of object (0)

TODO: Usage and meaning?
Buffer — p_info_items: Requested information items

Values of constants in Firebird’s inf_pub.h starting with isc_info_tra_ or fbinfo_tra_.
Int32 — p_info_buffer_length: Length of buffer available for receiving response

Too small may lead to receiving a truncated buffer, which necessitates requesting information again with a larger size.

The buffer in the response is sized to the actual length of the response (upto the declared available length), so specifying a larger than necessary size does not inflate the response on the wire.

Server

Generic response — on success, p_resp_data holds the requested information.

+ A truncated response is considered a success, and can only be determined by parsing p_resp_data.

5. Statements

5.1. Allocate

Allocates a statement handle on the server.

Client

Int32 — p_operation: Operation code (op_allocate_statement)
Int32 — p_rlse_object: Database handle

Server

Generic response — on success, p_resp_object is the allocated statement handle.

5.1.1. Deviations for protocol version 11

An op_allocate_statement can only be sent together with a Prepare operation.

This may not be entirely correct, and needs further verification.

5.2. Free

Frees resources held by the statement.

Client

Int32 — p_operation

Operation code (op_free_statement)

Int32 — p_sqlfree_statement

Statement handle

Int32 — p_sqlfree_option

Option Description

Option	Description
`DSQL_close — 1`	Closes the cursor opened after statement execute.
`DSQL_drop — 2`	Releases the statement handle.
`DSQL_unprepare — 4`	Firebird 2.5 or higher Close resources associated with statement handle, and unprepares the currently allocated statement text. The statement handle itself is retained. + It is not necessary to unprepare before preparing a new statement on the same handle.

DSQL_close — 1

Closes the cursor opened after statement execute.

DSQL_drop — 2

Releases the statement handle.

DSQL_unprepare — 4

Firebird 2.5 or higher
Close resources associated with statement handle, and unprepares the currently allocated statement text. The statement handle itself is retained.

+ It is not necessary to unprepare before preparing a new statement on the same handle.

Server

Generic response

5.2.1. Deviations for protocol version 11

Request flushing and response processing can be deferred for ptype_batch_send or higher.

For DSQL_drop and DSQL_unprepare, we recommend flushing immediately so the server at least processes the request, which will prevent longer than necessary retention of metadata locks. The response processing can then still be deferred until receiving the response of another action.

5.3. Prepare

Client

Int32 — p_operation

Operation code (op_prepare_statement)

Int32 — p_sqlst_transaction

Transaction handle

Int32 — p_sqlst_statement

Statement handle

Int32 — p_sqlst_SQL_dialect

SQL dialect (1 or 3)

This should generally match the connection dialect.

String — p_sqlst_SQL_str

Statement to be prepared

Buffer — p_sqlst_items

Describe and describe bind information items

Example of requested information items

isc_info_sql_select
isc_info_sql_describe_vars
isc_info_sql_sqlda_seq
isc_info_sql_type
isc_info_sql_sub_type
isc_info_sql_length
isc_info_sql_scale
isc_info_sql_field
isc_info_sql_relation

Int32 — p_sqlst_buffer_length

Target buffer length (32768)

Server

Generic response — on success, p_resp_data holds the statement description (matching the requested information items)

For statements with a lot of columns and/or parameters, it may be necessary to handle truncation of the buffer by repeating the describe and/or describe bind information request using Information request and using isc_info_sql_sqlda_start to inform the server from which column or parameter to continue.

For an example, see Jaybird’s StatementInfoProcessor.handleTruncatedInfo(…).

5.3.1. Deviations for protocol version 11

The statement handle can no longer be allocated separately. The initial Allocate operation must be sent together with the first prepare operation. When allocating and preparing together, the value of the statement handle of the prepare must be 0xFFFF (invalid object handle). The responses must be processed in order: first allocate response, then prepare response.

Once a statement handle has been allocated, it can be reused by sending a prepare with the obtained statement handle.

5.4. Describe

Requesting a description of output parameters (columns) of a query is done using the statement information request message

Example of requested information items

isc_info_sql_select
isc_info_sql_describe_vars
isc_info_sql_sqlda_seq
isc_info_sql_type
isc_info_sql_sub_type
isc_info_sql_length
isc_info_sql_scale
isc_info_sql_field
isc_info_sql_relation

The initial request can be done as part of Prepare. The information can be requested together with Describe bind (input parameters).

5.5. Describe bind (input parameters)

Describe of input parameters of a query is done using the statement information request message

Example of requested information items

isc_info_sql_select
isc_info_sql_describe_vars
isc_info_sql_sqlda_seq
isc_info_sql_type
isc_info_sql_sub_type
isc_info_sql_length
isc_info_sql_scale
isc_info_sql_field
isc_info_sql_relation

The initial request can be done as part of Prepare. The information can be requested together with Describe.

5.6. Execute

Client

Int32 — p_operation

Operation code

Operation Usage

Operation	Usage
`op_execute`	DDL and DML statements
`op_execute2`	Executable stored procedures, or singleton `RETURNING` (i.e. statements described as `isc_info_sql_stmt_exec_procedure`)

op_execute

DDL and DML statements

op_execute2

Executable stored procedures, or singleton RETURNING (i.e. statements described as isc_info_sql_stmt_exec_procedure)

Int32 — p_sqldata_statement

Statement handle

Int32 — p_sqldata_transaction

Transaction handle

Buffer — p_sqldata_blr

Parameters in BLR format

If there are no parameters, send a zero-length buffer.

Int32 — p_sqldata_message_number

Message number; unused, always use 0

Int32 — p_sqldata_messages

Number of messages — 1 if there are parameters, 0 if there are no parameters

Buffer — no name

Parameter values

If p_sqldata_messages is 0, this buffer must not be sent (not even as a zero-length buffer)

TODO: Might not even be a buffer, verify.

If using op_execute2 (the statement is a stored procedure and there are output parameters):

Buffer — p_sqldata_out_blr: Output parameters in BLR format
Int32 — p_sqldata_out_message_number: Output message number (0) ??

Additions in protocol 16 and higher

UInt32 — p_sqldata_timeout: Statement timeout value in milliseconds (0 — use connection-level statement timeout)

Additions in protocol 18 and higher

UInt32 — p_sqldata_cursor_flags

Cursor flags

CURSOR_TYPE_SCROLLABLE — 0x01

request scrollable cursor

Additions in protocol 19 and higher

UInt32-- p_sqldata_inline_blob_size: Maximum inline blob size

A value of 0 disables inline blobs. The server may use a lower limit than requested. In the Firebird 5.0.3 and Firebird 6 implementation at the time of writing, the server has a maximum of 65535 bytes.

TODO: Describe op_inline_blob somewhere

Server

For op_execute:

Generic response

For op_execute2:

Success response: SQL response followed by Generic response

Failure response: only Generic response

5.7. Rows affected by query execution

Obtaining the rows affected by a query is done using the statement information request message

List of requested information items

isc_info_sql_records

5.8. Fetch

Client

Int32 — p_operation: Operation code (op_fetch)
Int32 — p_sqldata_statement: Statement handle
Buffer — p_sqldata_blr: Output parameters in BLR format

Only needs to be sent on first fetch; subsequent fetches can send a zero-length buffer.
Int32 — p_sqldata_message_number: Message number (always 0)
Int32 — p_sqldata_messages: Message count/fetch size (e.g. 200)

The server may decide to return fewer rows than requested, even if the end-of-cursor wasn’t reached yet.

Server

Success response: one or more Fetch response

Failure response: Generic response — with an error in p_resp_status_vector

It is possible to receive Generic response with an error in the status vector after one or more fetch responses.

5.9. Set cursor name

Client

Int32 — p_operation: Operation code (op_set_cursor)
Int32 — p_sqlcur_statement: Statement handle
String — p_sqlcur_cursor_name: Cursor name (null terminated!)
Int32 — p_sqlcur_type: Cursor type

Reserved for future use, always use 0.

Server

Generic response

5.10. Information request

This is similar to Database information request.

Client

Int32 — p_operation: Operation code (op_info_sql)
Int32 — p_info_object: Statement handle
Int32 — p_info_incarnation: Incarnation of object (0)

TODO: Usage and meaning?
Buffer — p_info_items: Requested information items

Values of constants in Firebird’s inf_pub.h starting with isc_info_sql_.
Int32 — p_info_buffer_length: Length of buffer available for receiving response

Too small may lead to receiving a truncated buffer, which necessitates requesting information again with a larger size.

The buffer in the response is sized to the actual length of the response (upto the declared available length), so specifying a larger than necessary size does not inflate the response on the wire.

Server

Generic response — on success, p_resp_data holds the requested information.

+ A truncated response is considered a success, and can only be determined by parsing p_resp_data.

Information about how to parse the information buffer sent by the Firebird server can be found in the InterBase 6.0 documentation set

6. Blobs

6.1. Create/Open

Client

Int32 — p_operation

Operation code

Operation Description

Operation	Description
`op_create_blob`	Creates a new blob
`op_create_blob2`	Creates a new blob with a blob parameter buffer
`op_open_blob`	Opens an existing blob
`op_open_blob2`	Opens an existing blob with a blob parameter buffer

op_create_blob

Creates a new blob

op_create_blob2

Creates a new blob with a blob parameter buffer

op_open_blob

Opens an existing blob

op_open_blob2

Opens an existing blob with a blob parameter buffer

Buffer — p_blob_bpb

Blob parameter buffer

Only sent for op_create_blob2 and op_open_blob2

Int32 — p_blob_transaction

Transaction handle

Int64 — p_blob_id

Blob ID

Server

Generic response — on success

p_resp_object is the blob handle
p_resp_blob_id is the blob id (for op_create_blob / op_create_blob2 only)

6.1.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, other blob operations can be sent immediately after the open/create. They can use the invalid object handle 0xFFFF instead of the — not yet received — blob handle.

6.2. Get segment

Client

Int32 — p_operation: Operation code (op_get_segment)
Int32 — p_sgmt_blob: Blob handle
Int32 — p_sgmt_length: Segment length

Maximum length is 32767 for Firebird 2.5 and older, 65535 for Firebird 3.0 and higher.
Buffer — p_sgmt_segment: Always a zero-length buffer

Server

Generic response — on success, p_resp_data is the blob segment

The response buffer in p_resp_data contains zero or more segments. Each segment starts with 2-bytes for the length (little-endian), followed by that length of data.

6.2.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_get_segment can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF.

6.3. Put segment

Client

Int32 — p_operation: Operation code (op_put_segment)
Int32 — p_sgmt_blob: Blob handle
Int32 — p_sgmt_length: Length of segment data (effectively ignored; possibly only in recent Firebird versions)
Buffer — p_sgmt_segment: Blob segment

If the blob was created as a segmented blob, the maximum length is 32765 (Firebird 2.5 and older) or 65533 (Firebird 3.0 and higher).

For stream blobs, there is no length limitation other than the maximum buffer length (TODO: verify, might only be for recent versions).

Server

Generic response

6.3.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_put_segment can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF.

6.4. Batch segments

Similar to Put segment, but allows to send multiple segments.

Client

Int32 — p_operation: Operation code (op_batch_segments)
Int32 — p_sgmt_blob: Blob handle
Int32 — p_sgmt_length: Length of segment data (effectively ignored; possibly only in recent Firebird versions)
Buffer — p_sgmt_segment: Blob segments

The buffer can contain one or more segments, which are prefixed with 2 bytes of length (little endian), followed by the data. The maximum length per segment is 32765 (Firebird 2.5 and older) or 65533 (Firebird 3.0 and higher).

Server

Generic response

6.4.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_batch_segment can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF.

6.5. Seek

Seek is only supported for blobs that were created as a stream blob. Seek is not fully supported for blobs longer than 2 GiB (4 GiB?).

Client

Int32 — p_operation

Operation code (op_seek_blob)

Int32 — p_seek_blob

Blob handle

Int32 — p_seek_mode

Seek mode

`blb_seek_from_head` — `0`	absolute seek from start of blob
`blb_seek_relative` — `1`	relative seek from current position
`blb_seek_from_tail` — `2`	absolute seek from end of blob

Int32 — p_seek_offset

Offset

Server

Generic response — on success, p_resp_object is the current position.

6.5.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_seek_blob can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF.

6.6. Cancel

Cancels and invalidates the blob handle. If this was a newly created blob, the blob is disposed.

Client

Int32 — p_operation: Operation code (op_cancel_blob)
Int32 — p_rlse_object: Blob handle

Server

Generic response

6.6.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_cancel_blob can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF. Though doing this probably makes little sense for op_cancel_blob.

6.7. Close

Closes and invalidates the blob handle.

Client

Int32 — p_operation: Operation code (op_close_blob)
Int32 — p_rlse_object: Blob handle

Server

Generic response

6.7.1. Deviations for protocol version 11

Request flushing and response processing can be deferred.

If ptype_batch_send or higher is used, op_close_blob can be batched with Create/Open (and other blob operations) by using the invalid object handle 0xFFFF.

7. Arrays

7.1. Get slice

Client

Int32 — p_operation: Operation code (op_get_slice)
Int32 — p_slc_transaction: Transaction handle
Int64 — p_slc_id: Array handle
Int32 — p_slc_length: Slice length
Buffer — p_slc_sdl: Slice descriptor (SDL)
Buffer — p_slc_parameters: Slice parameters (always empty?, needs verification)
Buffer — p_slc_slice: Slice data (always empty)

Server

Success response: Slice response

Failure response: Generic response

7.2. Put slice

Client

Int32 — p_operation: Operation code (op_put_slice)
Int32 — p_slc_transaction: transaction handle
Int64 — p_slc_id: Array handle
Int32 — p_slc_length: Slice length
Buffer — p_slc_sdl: Slice descriptor (SDL)
Buffer — p_slc_parameters: Slice parameters (always empty?, needs verification)
Buffer` — p_slc_slice: Slice data

Server

Generic response — on success, p_resp_blob_id is the array handle.

8. Batches

Statement batches were introduced in protocol 16 (Firebird 4.0).

8.1. Create

Client

Int32 — p_operation: Operation code (op_batch_create)
Int32 — p_batch_statement: Statement handle
Buffer — p_batch_blr: BLR format of batch messages
UInt32 — p_batch_msglen: Message length
Buffer — p_batch_pb: Batch parameters buffer

If ptype_lazy or higher, flushing and response processing can be deferred.

Server

Generic response

8.2. Send messages

Client

Int32 — p_operation: Operation code (op_batch_msg)
Int32 — p_batch_statement: Statement handle
UInt32 — p_batch_messages: Number of messages
Buffer — p_batch_data: Batched values (formatted message repeats 'Number of messages' times)

Server

Generic response

8.3. Execute batch

Client

Int32 — p_operation: Operation code (op_batch_exec)
Int32 — p_batch_statement: Statement handle
Int32 — p_batch_transaction: Transaction handle

Server

Success response:

Int32 — p_operation: Operation code

If operation equals op_batch_cs:

Batch completion state

Int32 — p_batch_statement: Statement handle
UInt32 — p_batch_reccount: Total records count
UInt32 — p_batch_updates: Number of update counters (records updated per each message)
UInt32 — p_batch_vectors: Number of per-message error blocks (message number in batch and status vector of an error processing it)
UInt32 — p_batch_errors: Number of simplified per-message error blocks (message number in batch without status vector)
Byte[]: Update counters (records updated per each message), array of Int32, length is equal to p_batch_updates

Length is p_batch_updates * 4 bytes long.
Byte[]: Detailed info about errors in batch (for each error server sends number of message (Int32) and status vector in standard way (exactly like in op_response). Number of such pairs is equal to p_batch_vectors.

Length can only be determined by correctly parsing the <Int32><statusvector> pairs.
Byte[]: Simplified error blocks (for each error server sends number of message (Int32) w/o status vector). Used when too many errors took place. Number of elements is equal to p_batch_errors.

Length is p_batch_errors * 4 bytes.

Failure response: Generic response

8.4. Release batch

Client

Int32 — p_operation: Operation code (op_batch_rls)
Int32 — p_batch_statement: Statement handle

Server

Generic response

8.5. Cancel batch

Client

Int32 — p_operation: Operation code (op_batch_cancel)
Int32 — p_batch_statement: Statement handle

Server

Generic response

8.6. Sync batch

Introduced in protocol 17 (Firebird 4.0.2).

Used to force the server to acknowledge previously sent lazy intermediate operations (e.g. op_batch_msg, op_batch_regblob, op_batch_blob_stream and possibly others).

Client

Int32 — p_operation: Operation code (op_batch_sync)

Server

Generic response

8.7. Set default blob parameters

Client

Int32 — p_operation: Operation code (op_batch_set_bpb)
Int32 — p_batch_statement: Statement handle
Buffer — p_batch_blob_bpb: Default BLOB parameter buffer

Server

Generic response

8.8. Register existing blob

Client

Int32 — p_operation: Operation code (op_batch_regblob)
Int32 — p_batch_statement: Statement handle
Int64 — p_batch_exist_id: Existing BLOB ID
Int64 — p_batch_blob_id: Batch temporary BLOB ID

Server

Generic response

8.9. Stream of BLOB data

This description needs further verification and possibly correction. For example, it seems to mix up Buffer and Byte[]. We’re also not able to match some fields to the implementation. For example, the repeated "Record length" seems to be absent, or may actually refer to the p_batch_blob_data buffer length.

Client

Int32 — p_operation

Operation code (op_batch_blob_stream)

Int32 — p_batch_statement

Statement handle

Buffer[] — p_batch_blob_data

BLOB stream

This stream is a sequence of blob records. Each blob records contains:

UInt32: Record length

The following three fields are called BLOB header
Int64: Batch temporary BLOB ID
UInt32: BLOB size
UInt32: BLOB parameters buffer size
Buffer: BLOB parameters buffer
Buffer: BLOB data (length - BLOB size bytes) (what does this mean?)

BLOB headers and records in a stream need not match, i.e. one record may contain many BLOBs and BLOB may stretch from one record to next.

Server

Generic response

9. Services

9.1. Attach

This is essentially the same as database attach, but with op_service_attach.

Client

Int32 — p_operation: Operation code (op_service_attach)
Int32 — p_atch_database: Database object id; currently always 0
String — p_atch_file: Service name

Current Firebird versions only support one service: service_mgr. Since Firebird 3.0, this can also be an empty string (empty buffer) with the same meaning.

The encoding is unspecified, but given the only valid name is either ASCII or empty, use of ASCII or an ASCII-compatible encoding (e.g. UTF-8 or extended ANSI code pages) should always work.
Buffer — p_atch_dpb: Service parameter buffer

Similar to the database parameter buffer of database attach/create, but using isc_spb_ tags instead of isc_dpb_.

Server

Generic response

9.2. Detach

Client

Int32 — p_operation: Operation code (op_service_detach)
Int32 — p_rlse_object: Service manager attachment handle (always 0)

Server

Generic response

9.3. Start

Client

Int32 — p_operation: Operation code (op_service_start)
Int32 — p_info_object: Service manager attachment handle (always 0)
Int32 — p_info_incarnation: Incarnation of object (0)

TODO: Usage and meaning?
Buffer — p_info_items: Service parameter buffer

Server

Generic response

9.4. Query service

Client

Int32 — p_operation: Operation code (op_service_info)
Int32 — p_info_object: Service manager attachment handle
Int32 — p_info_incarnation: Incarnation of object (0)

TODO: Usage and meaning?
Buffer — p_info_items: Service parameter buffer
Buffer — p_info_recv_items: Requested information items
Int32 — p_info_buffer_length: Requested information items buffer length

Server

Generic response — on success, p_resp_data contains the requested information.

10. Events

10.1. Connection request

Client

Int32 — p_operation: Operation code (op_connect_request)
Int32 — p_req_type: Unused, but always use P_REQ_async (1) for backwards compatibility
Int32 — p_req_object: Unused, always use 0
Int32 — p_req_partner: Unused, always use 0

Server

Generic response — with on success:

p_resp_data

Aux connection information

This is part of the sockaddr_in structure.

It is not in XDR format

Int16: Socket family (can be ignored)
Int16: Aux connection port
Remaining bytes: To be ignored: always use the hostname or IP address of the original connection.

After a successful response, the client needs to create a connection to the specified port.

10.2. Queue events

Client

Int32 — p_operation: Operation code (op_que_events)
Int32 — p_event_database: Database handle
Buffer — p_event_items: Events parameter buffer
Int32 — p_event_ast: Unused, always set 0
Int32 — p_event_arg: Unused, always set 0
Int32 — p_event_rid: Local event id

Server

Generic response — on success, p_resp_object holds the remote event id.

10.3. Cancel events

Client

Int32 — p_operation: Operation code (op_cancel_events)
Int32 — p_event_database: Database handle (always 0)
Int32 — p_event_rid: Local event id

Server

Generic response

11. Reading row data

TODO: Processing row data

Appendix A: External Data Representation (XDR)

The Firebird wire protocol uses XDR for exchange messages between client and server.

Appendix B: Data types

Int32

Integer 32-bits

In some cases — e.g. object handles, and some lengths — this is actually a 16-bit short encoded as a 32-bit int with the high bits zero.

UInt32

Unsigned integer 32-bits

Int64

Integer 64-bits

Alternatively, especially for blob and arrays ids, can be interpreted as two Int32, a.k.a. a “quad”. Interpretation as a 64-bit integer — even for blob and array ids — is generally simpler, and should not make a difference.

Buffer

Composed of

Int32

Length of buffer data without padding

Byte[]

Buffer data

Byte[]

Padding of 0 to 3 bytes to align the message to a multiple of 4 (e.g. calculated as (4 - length) & 3)).

That is, for some N >= 0, when the buffer length is:

N * 4 bytes → no padding
N * 4 + 1 bytes → 3 bytes padding
N * 4 + 2 bytes → 2 bytes padding
N * 4 + 3 bytes → 1 byte padding

Byte[]

An array of bytes

Length follows from another field in the message, from correct parsing of the value, or from other specifics of the message.

String

A text string, read or written as a Buffer, encoded in the connection character set or some message or context specific character set

Appendix C: Revision history

Revision History

Revision History
0.1	31 May 2004		First draft for review.
0.2	02 Jun 2004		Fixed issues reported by Paul Vinkenoog.
0.3	03 Jun 2004		Added new subsections to the Statements section.
0.4	05 Jun 2004		Fixed issues reported by Paul Vinkenoog.
0.5	06 Jun 2004		Fixed issues reported by Paul Vinkenoog.
0.6	07 Jun 2004		Added events system documentation.
0.7	16 Jun 2004		Modifed document ID to wireprotocol.
0.8	17 Jun 2004		Added two new segmendted lists.
0.9	18 Jun 2004		Improved segmentedlist usage. Fixed rendering of important tags.
0.10	19 Jun 2004		Changed rendering of important tags using Paul Vinkenoog fix.
0.11	20 Jun 2004		Added new segmentedlist. Updated Statements.Prepare documentation. Updated Statements.Execute documentation. Updated Blobs.GetSegment documentation. Updated Blobs.Seek documentation.
0.12	21 Jun 2004		Updated services information.
0.13	13 Sep 2014		Updated and expanded protocol information
0.14	04 Aug 2020	MR	Conversion to AsciiDoc, minor copy-editing
0.15	26 Dec 2021	AP	Document batch execution
0.16	13 Apr 2025	MR	Added Firebird struct field names to message descriptions for reference Updated, corrected and expanded field descriptions Documented `op_put_segment` Added missing field in `p_sgmt_length` in `op_batch_segments` Documented protocol 11 batching of operations for blobs Documented protocol 16 timeout (`p_sqldata_timeout`) for `op_execute`/`op_execute2` Documented protocol 18 cursor flags (`p_sqldata_cursor_flags`) for `op_execute`/`op_execute2` Documented protocol 19 inline blob size (`p_sqldata_inline_blob_size`) for `op_execute`/`op_execute2` (but not yet `op_inline_blob`!)

0.1

31 May 2004

First draft for review.

0.2

02 Jun 2004

Fixed issues reported by Paul Vinkenoog.

0.3

03 Jun 2004

Added new subsections to the Statements section.

0.4

05 Jun 2004

Fixed issues reported by Paul Vinkenoog.

0.5

06 Jun 2004

Fixed issues reported by Paul Vinkenoog.

0.6

07 Jun 2004

Added events system documentation.

0.7

16 Jun 2004

Modifed document ID to wireprotocol.

0.8

17 Jun 2004

Added two new segmendted lists.

0.9

18 Jun 2004

Improved segmentedlist usage.
Fixed rendering of important tags.

0.10

19 Jun 2004

Changed rendering of important tags using Paul Vinkenoog fix.

0.11

20 Jun 2004

Added new segmentedlist.
Updated Statements.Prepare documentation.
Updated Statements.Execute documentation.
Updated Blobs.GetSegment documentation.
Updated Blobs.Seek documentation.

0.12

21 Jun 2004

Updated services information.

0.13

13 Sep 2014

Updated and expanded protocol information

0.14

04 Aug 2020

Conversion to AsciiDoc, minor copy-editing

0.15

26 Dec 2021

Document batch execution

0.16

13 Apr 2025

Added Firebird struct field names to message descriptions for reference
Updated, corrected and expanded field descriptions
Documented op_put_segment
Added missing field in p_sgmt_length in op_batch_segments
Documented protocol 11 batching of operations for blobs
Documented protocol 16 timeout (p_sqldata_timeout) for op_execute/op_execute2
Documented protocol 18 cursor flags (p_sqldata_cursor_flags) for op_execute/op_execute2
Documented protocol 19 inline blob size (p_sqldata_inline_blob_size) for op_execute/op_execute2 (but not yet op_inline_blob!)

Firebird Wire Protocol

1. Introduction

2. Responses

2.1. Generic response

2.2. SQL response

2.3. Fetch response

2.4. Slice response

3. Databases

3.1. Attach

3.1.1. Identification

Client

Server

3.1.2. Attachment

Client

Server

3.2. Detach

Client

Server

3.3. Create

Client

Server

The CREATE DATABASE statement

3.4. Drop

Client

Server

3.5. Database information request

Client

Server

3.6. Disconnect

Client

4. Transactions

4.1. Start transaction

Client

Server

The SET TRANSACTION statement

4.2. Commit transaction

Client

Server

4.3. Rollback transaction

Client

Server

4.4. Commit retaining

Client

Server

4.5. Rollback retaining

Client

Server

4.6. Prepare

4.6.1. Simple prepare

Client

Server

4.6.2. Prepare with message

Client

Server

4.7. Transaction information request

Client

Server

5. Statements

5.1. Allocate

Client

Server

5.1.1. Deviations for protocol version 11

5.2. Free

Client

Server

5.2.1. Deviations for protocol version 11

5.3. Prepare

Client

Server

5.3.1. Deviations for protocol version 11

5.4. Describe

5.5. Describe bind (input parameters)

5.6. Execute

Client

Additions in protocol 16 and higher

Additions in protocol 18 and higher

Additions in protocol 19 and higher

Server

5.7. Rows affected by query execution

5.8. Fetch

The `CREATE DATABASE` statement

The `SET TRANSACTION` statement