> For the complete documentation index, see [llms.txt](https://sandbox-docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sandbox-docs.verifone.com/s-adk-5.1-programmers-guide/readme/modules/group__sdilowlevel.md).
# Low level message interface
[Functions](#func-members)
| | |
| --------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Functions | |
| int | [sendMessage](#ga9469453c091c21eb8ea86f57891b7308) (unsigned short cmd, unsigned short p1p2, const [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&data) |
| int | [sendMessage](#ga45c151464c9a5da87cec4f15434eac64) (unsigned short cmd, const [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&data) |
| int | [receiveMessage](#ga6c1ca6f917bb545fa12b98bafddeb839) (unsigned short \&sw1sw2, [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&data) |
| int | [sendReply](#gaf1a6553edbb1cf8a3923c00549aaf322) (unsigned short cmd, const [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&data) |
| int | [sendReceiveMessage](#ga6ecd2e2678b30d7eae0dee49978116a0) (unsigned short cmd, unsigned short p1p2, const [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&sdata, unsigned short \&sw1sw2, [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&rdata) |
| int | [sendReceiveMessage](#ga61e51cf697228a812dd47cd53e7ca3b0) (unsigned short cmd, const [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&sdata, unsigned short \&sw1sw2, [bytevector](https://github.com/verifoneone/verifone-git-book-adk/tree/ADK5.1_staging/classvfisdi_1_1_s_d_i_client.md#a64b5be62be31dcda165d2c6c3c262fb5) \&rdata) |
### DetailedDescription
### FunctionDocumentation
### receiveMessage()
int receiveMessage
receive SDI reply with internal handling of SDI callbacks.
**Parameters**
\[out] **sw1sw2** SW1 SW2 packed into an unsigned short as returned from SDI \[out] **data** reply data
#### Returns
SDI error code ([Result](/s-adk-5.1-programmers-guide/readme/namespaces/namespacevfisdi.md#a28287671eaf7406afd604bd055ba4066))
### sendMessage()\[1/2]
int sendMessage
inline
send SDI command with P1P2=0x0000
**Parameters**
\[in] **cmd** class and instruction of the command to be sent \[in] **data** command data
#### Returns
SDI error code ([Result](/s-adk-5.1-programmers-guide/readme/namespaces/namespacevfisdi.md#a28287671eaf7406afd604bd055ba4066))
### sendMessage()\[2/2]
int sendMessage
send SDI message
**Parameters**
\[in] **cmd** class and instruction of the command to be sent \[in] **p1p2** P1 and P2 of the command to be sent \[in] **data** command data
#### Returns
SDI error code ([Result](/s-adk-5.1-programmers-guide/readme/namespaces/namespacevfisdi.md#a28287671eaf7406afd604bd055ba4066))
### sendReceiveMessage()\[1/2]
int sendReceiveMessage
inline
### sendReceiveMessage()\[2/2]
int sendReceiveMessage
send and receive SDI message
**Parameters**
\[in] **cmd** class and instruction of the command to be sent \[in] **p1p2** P1 and P2 of the command to be sent \[in] **sdata** command data \[out] **sw1sw2** SW1 SW2 packed into an unsigned short as returned from SDI \[out] **rdata** reply data
#### Returns
SDI error code ([Result](/s-adk-5.1-programmers-guide/readme/namespaces/namespacevfisdi.md#a28287671eaf7406afd604bd055ba4066))
### sendReply()
int sendReply
send SDI reply for an SDI callback message
**Parameters**
\[in] **cmd** class and instruction of the reply to be sent \[in] **data** command data
#### Returns
0 in case of success, -1 in case of failure
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