# Asyncronous Socket Management

    /*
    **	(c) COPYRIGHT MIT 1995.
    **	Please first read the full copyright statement in the file COPYRIGH.
    */

This module contains the routines for handling the set of active sockets currently in use by the multithreaded clients. It is an internal module to the Library, the application interface is implemented in the Event Module. Look for more information in the Multithread Specifications.

This module is implemented by HTNet.c, and it is a part of the W3C Reference Library.

    #ifndef HTNET_H
    #define HTNET_H
    #include "HTEvntrg.h"
    #include "HTReq.h"

## The HTNet Object

The `HTNet` object is the core of the request queue management. This object contains information about the socket descriptor, the input read buffer etc. required to identify and service a request.

    typedef struct _HTNet HTNet;

## Request Call Back Functions

Callback functions can be registered to be called before and after a request has either been started or has terminated. The following functions are the generic registration mechanisms where we use lists as the basic data container. Then there is two methods for binding a list of callback functions to the set which is called before and to the set set which is called after

In both cases there can be more than one callback function which are called on turn and each callback function can be associated with a status code of the request. For example one callback function can be registered for HT_LOADED, another for HT_ERROR etc.

### Register a Request Callback

Register a call back function that is to be called on every termination of a request. Several call back functions can be registered in which case all of them are called in the reverse order of which they were registered (last one first). We name the calling mechansm of calling the functions for the before loop and the after loop.

In case the callback function is registered as being called after the request has terminated the result of the request is passed to the fucntion. The status signifies which call back function to call depending of the result of the request. This can be

HT_ERROR
  An error occured
HT_LOADED
  The document was loaded
HT_NO_DATA
  OK, but no data
HT_RETRY
  Retry request after at a later time
HT_REDIRECT
  The request has been redirected and we send back the new URL
HT_ALL
  All of above

Any callback function any code it likes, but IF NOT the code is HT_OK, then the callback loop is stopped. If we are in the before loop and a function returns anything else than HT_OK then we immediately jump to the after loop passing the last return code from the before loop.

    typedef int HTNetCallback (HTRequest * request, int status);

    extern BOOL HTNetCall_add (HTList * list, HTNetCallback *cbf, int status);

### Delete a single Callbak

Removes a callback function from a list

    extern BOOL HTNetCall_delete (HTList * list, HTNetCallback *cbf);

### Delete a list of Callbacks

Unregisters all call back functions in the list

    extern BOOL HTNetCall_deleteAll (HTList * list);

### Call List of Registered Callback Functions

Call all the call back functions registered in the list IF not the status is HT_IGNORE. The callback functions are called in the order of which they were registered. At the moment an application callback function is called, it can free the request object - it is no longer used by the Library. Returns what the last callback function returns

    extern int HTNetCall_execute (HTList * list, HTRequest * request, int status);

### BEFORE Callbacks

Global set of callback functions BEFORE the request is issued. The list can be NULL.

    extern BOOL HTNetCall_addBefore	(HTNetCallback *cbf, int status);
    extern BOOL HTNet_setBefore	(HTList * list);
    extern HTList * HTNet_before	(void);
    extern int HTNet_callBefore	(HTRequest *request, int status);

### AFTER Callbacks

Global set of callback functions AFTER the request is issued. The list can be NULL

    extern BOOL HTNetCall_addAfter	(HTNetCallback *cbf, int status);
    extern BOOL HTNet_setAfter	(HTList * list);
    extern HTList * HTNet_after	(void);
    extern int HTNet_callAfter	(HTRequest *request, int status);

## Request Queue

The request queue ensures that no more than a fixed number of TCP connections are open at the same time. If more requests are handed to the Library, they are put into the pending queue and initiated when sockets become free.

### Number of Simultanous open TCP connections

Set the max number of simultanous sockets. The default value is HT_MAX_SOCKETS which is 6. The number of persistent connections depend on this value as a deadlock can occur if all available sockets a persistent (see the DNS Manager for more information on setting the number of persistent connections). The number of persistent connections can never be more than the max number of sockets-2, so letting newmax=2 prevents persistent sockets.

    extern BOOL HTNet_setMaxSocket (int newmax);
    extern int  HTNet_maxSocket (void);

### List Active Queue

Returns the list of active requests that are currently having an open connection. Returns list of HTNet objects or NULL if error.

    extern HTList *HTNet_activeQueue (void);
    extern BOOL HTNet_idle (void);

### Are we Active?

We have some small functions that tell whether there are registered requests in the Net manager. There are tree queues: The active, the pending, and the persistent. The active queue is the set of requests that are actively sending or receiving data. The pending is the requests that we have registered but which are waiting for a free socket. The Persistent queue are requets that are waiting to use the same socket in order to save network resoures (if the server understands persistent connections).

#### Active Reqeusts?

Returns whether there are requests in the active queue or not

    extern BOOL HTNet_idle (void);

#### Registered Requests?

Returns whether there are requests registered in any of the lists or not

    extern BOOL HTNet_isEmpty (void);

### List Pending Queue

Returns the list of pending requests that are waiting to become active. Returns list of HTNet objects or NULL if error

    extern HTList *HTNet_pendingQueue (void);

## Create an Object

You can create a new HTNet object as a new request to be handled. If we have more than HTMaxActive connections already then put this into the pending queue, else start the request by calling the call back function registered with this access method. Returns YES if OK, else NO

    extern BOOL HTNet_newClient (HTRequest * request);

You can create a new HTNet object as a new request to be handled. If we have more than HTMaxActive connections already then return NO. Returns YES if OK, else NO

    extern BOOL HTNet_newServer (HTRequest * request, SOCKET sockfd, char *access);

And you can create a plain new HTNet object using the following method:

    extern HTNet * HTNet_new (HTRequest * request, SOCKET sockfd);

### Duplicate an Existing Object

Creates a new HTNet object as a duplicate of the same request. Returns YES if OK, else NO.

    extern HTNet * HTNet_dup (HTNet * src);

## HTNet Object Methods

### Make an Object Wait

Let a net object wait for a persistent socket. It will be launched from the HTNet_delete() function when the socket gets free.

    extern BOOL HTNet_wait (HTNet *net);

### Priority Management

Each HTNet object is created with a priority which it inherits from the Request manager. However, in some stuations it is useful to be to change the current priority after the request has been started. These two functions allow you to do this. The effect will show up the first time (which might be imidiately) the socket blocks and control returns to the event loop. Also have a look at how you can do this before the request is issued in the request manager.

    extern HTPriority HTNet_priority (HTNet * net);
    extern BOOL HTNet_setPriority (HTNet * net, HTPriority priority);

### Delete an Object

Deletes the HTNet object from the list of active requests and calls any registered call back functions IF not the status is HT_IGNORE. This is used if we have internal requests that the app doesn't know about. We also see if we have pending requests that can be started up now when we have a socket free. The callback functions are called in the reverse order of which they were registered (last one first);

    extern BOOL HTNet_delete (HTNet * me, int status);

### Delete ALL HTNet Objects

Deletes all HTNet object that might either be active or pending We DO NOT call the call back functions - A crude way of saying goodbye!

    extern BOOL HTNet_deleteAll (void);

### Kill a Request

Kill the request by calling the call back function with a request for closing the connection. Does not remove the object. This is done by HTNet_delete() function which is called by the load routine. Returns OK if success, NO on error

    extern BOOL HTNet_kill (HTNet * me);

### Kill ALL requests

Kills all registered (active+pending) requests by calling the call back function with a request for closing the connection. We do not remove the HTNet object as it is done by HTNet_delete(). Returns OK if success, NO on error

    extern BOOL HTNet_killAll (void);

## Data Access Methods

### Socket Descriptor

    extern BOOL HTNet_setSocket (HTNet * net, SOCKET sockfd);
    extern SOCKET HTNet_socket (HTNet * net);

    #endif /* HTNET_H */

End of declaration module