Inside Macintosh: Open Transport /

Chapter 3 - Endpoints / Endpoints Reference

Functions / Obtaining Information About an Endpoint

OTLook

Determines the current asynchronous event pending for an endpoint.

C INTERFACE

OTResult OTLook(EndpointRef ref);

C++ INTERFACE

OTResult TEndpoint::Look();

PARAMETERS

ref

The endpoint reference of the endpoint.

DESCRIPTION

You use the OTLook function in one of two cases. First, if the endpoint is in synchronous mode, you can call the OTLook function to poll for incoming data or connection requests. Second, certain asynchronous events might cause a synchronous function to fail with the result kOTLookErr. For example, if you call OTAccept and the endpoint gets a T_DISCONNECT event, the OTAccept function returns with kOTLookErr. In this case, you need to call the OTLook function to determine what event caused the original function to fail. Table 3-7 on page 3-25 lists the functions that might return the kOTLookErr result and the events that can cause these functions to fail.

The OTLook function returns an integer value that specifies the asynchronous event pending for the endpoint specified by the ref parameter. On error, OTLook returns a negative integer corresponding to a result code.

If there are multiple events pending, the OTLook function first looks for one of the following events: T_LISTEN, T_CONNECT, T_DISCONNECT, T_UDERR, or T_ORDREL. If it finds more than one of these, it returns them to you in first-in, first-out order. After processing these events, the OTLook function looks for the T_DATA, T_REQUEST, and T_REPLY events. If it finds more than one of these, it returns them to you in first-in, first-out order. You cannot use the OTLook function to poll for completion events.

Unless you are operating exclusively in synchronous mode, it is recommended that you use notifier functions to get information about pending events for an endpoint.

VALID STATES

All

SEE ALSO

For additional information on asynchronous processing and on handling asynchronous and completion events, see the section "Handling Events for Endpoints," beginning on page 3-22 and the chapter "Providers" in this book.

Table 3-7 on page 3-25 lists the functions that might return the kOTLookErr result and the events that can cause these functions to fail.

The reference section of the chapter "Providers" in this book lists values returned for pending asynchronous events and describes their meanings.

For information on how to use this function with a TCP/IP protocol, see page 8-16 in the TCP/IP chapter.