60 Serial Link Manager

This chapter provides reference material for the serial link manager API. The header file SerialLinkMgr.h declares the serial link manager API. For more information on the serial link manager, see the chapter "Serial Communication" in the Palm OS Programmer's Companion.

Serial Link Manager Functions

SlkClose

Purpose

Close down the serial link manager.

Prototype

Err SlkClose (void)

Parameters

None.

Result

0

No error.

slkErrNotOpen

The serial link manager was not open.

Comments

When the open count reaches zero, this routine frees resources allocated by serial link manager.

SlkCloseSocket

Purpose

Closes a socket previously opened with SlkOpenSocket.

The caller is responsible for closing the communications library used by this socket, if necessary.

Prototype

Err SlkCloseSocket (UInt16 socket)

Parameters

socket

The socket ID to close.

Result

0

No error.

slkErrSocketNotOpen

The socket was not open.

Comments

SlkCloseSocket frees system resources the serial link manager allocated for the socket. It does not free resources allocated and passed by the client, such as the buffers passed to SlkSetSocketListener; this is the client's responsibility. The caller is also responsible for closing the communications library used by this socket.

See Also

SlkOpenSocket

SlkFlushSocket

Purpose

Flush the receive queue of the communications library associated with the given socket.

Prototype

Err SlkFlushSocket (UInt16 socket, Int32 timeout)

Parameters

-> socket

Socket ID.

-> timeout

Interbyte timeout in system ticks.

Result

0

No error.

slkErrSocketNotOpen

The socket wasn't open.

SlkOpen

Purpose

Initialize the serial link manager.

Prototype

Err SlkOpen (void)

Parameters

None.

Result

0

No error.

slkErrAlreadyOpen

No error.

Comments

Initializes the serial link manager, allocating necessary resources. Return codes of 0 (zero) and slkErrAlreadyOpen both indicate success. Any other return code indicates failure. The slkErrAlreadyOpen function informs the client that someone else is also using the serial link manager. If the serial link manager was successfully opened by the client, the client needs to call SlkClose when it finishes using the serial link manager.

SlkOpenSocket

Purpose

Open a serial link socket and associate it with a communications library. The socket may be a known static socket or a dynamically assigned socket.

Prototype

Err SlkOpenSocket (UInt16 portID, UInt16 *socketP, Boolean staticSocket)

Parameters

portID

Comm library reference number for socket.

socketP

Pointer to location for returning the socket ID.

staticSocket

If TRUE, *socketP contains the desired static socket number to open. If FALSE, any free socket number is assigned dynamically and opened.

Result

0

No error.

slkErrOutOfSockets

No more sockets can be opened.

Comments

The communications library must already be initialized and opened (see SerOpen). When finished using the socket, the caller must call SlkCloseSocket to free system resources allocated for the socket. For information about well-known static socket IDs, see The Serial Link Protocol.

SlkReceivePacket

Purpose

Receive and validate a packet for a particular socket or for any socket. Check for format and checksum errors.

Prototype

Err SlkReceivePacket (UInt16 socket, Boolean andOtherSockets, SlkPktHeaderPtr headerP, void* bodyP, UInt16 bodySize, Int32 timeout)

Parameters

-> socket

The socket ID.

-> andOtherSockets

If TRUE, ignore destination in packet header.

<-> headerP

Pointer to the packet header buffer (size of SlkPktHeaderType).

<-> bodyP

Pointer to the packet client data buffer.

-> bodySize

Size of the client data buffer (maximum client data size which can be accommodated).

-> timeout

Maximum number of system ticks to wait for beginning of a packet; -1 means wait forever.

Result

0

No error.

slkErrSocketNotOpen

The socket was not open.

slkErrTimeOut

Timed out waiting for a packet.

slkErrWrongDestSocket

The packet being received had an unexpected destination.

slkErrChecksum

Invalid header checksum or packet CRC-16.

slkErrBuffer

Client data buffer was too small for packet's client data.

If andOtherSockets is FALSE, this routine returns with an error code unless it gets a packet for the specific socket.

If andOtherSockets is TRUE, this routine returns successfully if it sees any incoming packet from the communications library used by socket.

Comments

You may request to receive a packet for the passed socket ID only, or for any open socket which does not have a socket listener. The parameters also specify buffers for the packet header and client data, and a timeout. The timeout indicates how long the receiver should wait for a packet to begin arriving before timing out. If a packet is received for a socket with a registered socket listener, it will be dispatched via its socket listener procedure. On success, the packet header buffer and packet client data buffer is filled in with the actual size of the packet's client data in the packet header's bodySize field.

SlkSendPacket

Purpose

Send a serial link packet via the serial output driver.

Prototype

Err SlkSendPacket (SlkPktHeaderPtr headerP, SlkWriteDataPtr writeList)

Parameters

<-> headerP

Pointer to the packet header structure with client information filled in (see Comments).

-> writeList

List of packet client data blocks (see Comments).

Result

0

No error.

slkErrSocketNotOpen

The socket was not open.

slkErrTimeOut

Handshake timeout.

Comments

SlkSendPacket stuffs the signature, client data size, and the checksum fields of the packet header. The caller must fill in all other packet header fields. If the transaction ID field is set to 0 (zero), the serial link manager automatically generates and stuffs a new non-zero transaction ID. The array of SlkWriteDataType structures enables the caller to specify the client data part of the packet as a list of noncontiguous blocks. The end of list is indicated by an array element with the size field set to 0 (zero). This call blocks until the entire packet is sent out or until an error occurs.

SlkSetSocketListener

Purpose

Register a socket listener for a particular socket.

Prototype

Err SlkSetSocketListener (UInt16 socket, SlkSocketListenPtr socketP)

Parameters

-> socket

Socket ID.

-> socketP

Pointer to a SlkSocketListenType structure.

Result

0

No error.

slkErrBadParam

Invalid parameter.

slkErrSocketNotOpen

The socket was not open.

Comments

Called by applications to set up a socket listener.

Since the serial link manager does not make a copy of the SlkSocketListenType structure, but instead saves the passed pointer to it, the structure

• must not be an automatic variable (that is, local variable allocated on the stack)
  
  
• may be a global variable in an application
  
  
• may be a locked chunk allocated from the dynamic heap
  

The SlkSocketListenType structure specifies pointers to the socket listener procedure and the data buffers for dispatching packets destined for this socket. Pointers to two buffers must be specified: the packet header buffer (size of SlkPktHeaderType), and the packet body (client data) buffer. The packet body buffer must be large enough for the largest expected client data size. Both buffers may be application global variables or locked chunks allocated from the dynamic heap.

The socket listener procedure is called when a valid packet is received for the socket. Pointers to the packet header buffer and the packet body buffer are passed as parameters to the socket listener procedure.

---

NOTE:  

The application is responsible for freeing the SlkSocketListenType structure or the allocated buffers when the socket is closed. The serial link manager doesn't do it.

---

SlkSocketPortID

Purpose

Get the port ID associated with a particular socket; for use with the new serial manager.

Prototype

Err SlkSocketPortID (UInt16 socket, UInt16 * portIDP)

Parameters

-> socket

The socket ID.

<-> portIDP

Pointer to location for returning the port ID.

Result

0

No error.

slkErrSocketNotOpen

The socket was not open.

Compatibility

Implemented only if New Serial Manager Feature Set is present.

SlkSocketSetTimeout

Purpose

Set the interbyte packet receive-timeout for a particular socket.

Prototype

Err SlkSocketSetTimeout (UInt16 socket, Int32 timeout)

Parameters

-> socket

Socket ID.

-> timeout

Interbyte packet receive-timeout in system ticks.

Result

0

No error.

slkErrSocketNotOpen

The socket was not open.