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Inside Macintosh: Networking With Open Transport / Part 2 - Open Transport Reference

Chapter 22 - Endpoints Reference / Constants and Data Types

The TEndpointInfo Structure

The TEndpointInfo structure, which is returned by the OTGetEndpointInfo function, describes the initial characteristics of an endpoint that you opened by calling the OTOpenEndpoint function or the OTAsyncOpenEndpoint function . These functions initialize the supplied TEndpointInfo structure, if you have allocated space for one. You can also get a copy to the TEndpointInfo structure by calling the OTGetEndpointInfo function.

You use the TEndpointInfo structure to find out how large a buffer you must allocate to send or receive information for the endpoint and what kind of services the endpoint provides.

IMPORTANT

It is recommended that you do not hard-code values into your application that you could otherwise get from the endpoint's TEndpointInfo field. These values might change.

The TEndpointInfo structure is defined by the TEndpointInfo data type.

struct TEndpointInfo
{
   SInt32   addr;       
   SInt32   options;    
   SInt32   tsdu;       
   SInt32   etsdu;      
   SInt32   connect;    
   SInt32   discon;     
   UInt32   servtype;   
   UInt32   flags;      
};
typedef struct TEndpointInfo TEndpointInfo;

Field Description

addr

A value greater than or equal to 0 indicates the maximum size (in bytes) of a protocol address to which you can bind this endpoint. A value of T_INVALID indicates that this endpoint does not allow access to protocol addresses (e.g. serial communication). However, it does not account for protocols where the address is allowed to be a string, such as a DNS name for TCP/IP or an NBP name for AppleTalk. If you are using this feature, you have to be prepared to allow for a larger address size.

options

A value greater than or equal to 0 indicates the maximum number of bytes needed to store the protocol-specific options that this endpoint supports, if any. A value of T_INVALID (-2) indicates that this endpoint has no protocol-specific options that you can set; they are read-only. A value of -3 specifies that the provider does not support any options.

tsdu

For a transactionless endpoint, a positive value indicates the maximum number of bytes in a transport service data unit (TSDU) for this endpoint. A value of T_INFINITE (-1) indicates that there is no limit to the size of a TSDU. A value of 0 indicates that the provider does not support the concept of a TSDU. This means that you cannot send data with logical boundaries preserved across a connection. A value of T_INVALID indicates that this endpoint cannot transfer normal data (as opposed to expedited data).

For a transaction-based endpoint, this field indicates the maximum number of bytes in a response.

etsdu

For a transactionless endpoint, a positive value indicates the maximum number of bytes in an expedited transport service data unit (ETSDU) for this endpoint. A value of T_INFINITE indicates that there is no limit to the size of a ETSDU. A value of 0 indicates that this endpoint does not support the concept of an ETSDU. This means that you must not send expedited data with logical boundaries preserved across a connection. A value of T_INVALID indicates that this endpoint cannot transfer expedited data.

For a transaction-based endpoint, this field indicates the maximum number of bytes in a request.

connect

For a connection-oriented endpoint, a value greater than or equal to 0 indicates the maximum amount of data (in bytes) that you can send with the OTConnect function or the OTAccept function. A value of T_INVALID indicates that this endpoint does not let you send data with these functions. This field is meaningless for other types of endpoints.

discon

For a connection-oriented endpoint, a value greater than or equal to 0 indicates the maximum amount of data (in bytes) that you can send using the OTSndDisconnect function. A value of T_INVALID indicates that this endpoint does not let you send data with disconnection requests. This field is meaningless for other types of endpoints.

servtype

A constant that indicates what kind of service the endpoint provides. Possible values are given by the endpoint service enumeration.

flags

A bit field that provides additional information about the endpoint. Possible values are given by the endpoint flags enumeration.