/Net/dxcern/userd/timbl/hypertext/WWW/Library/src/HTTCP.html

Generic Network Communication

This module has the common code for handling TCP/IP and DECnet connections etc. The module is a part of the CERN Common WWW Library. 
#ifndef HTTCP_H
#define HTTCP_H

#include "HTUtils.h"
#include "HTAccess.h"

#ifdef SHORT_NAMES
#define HTInetStatus		HTInStat
#define HTInetString 		HTInStri
#define HTParseInet		HTPaInet
#endif

Connection Management

All connections are established through these two functions.

Active Connection Establishment

This makes an active connect to the specified host. The HTNetInfo structure is parsed in order to handle errors. Default port might be overwritten by any port indication in the URL specified as <host>:<port> If it is a multihomed host then HTDoConnect measures the time to do the connection and updates the calculated weights in the cache of visited hosts. 
PUBLIC int HTDoConnect PARAMS((	HTNetInfo  	*net,
				char		*url,
			     	u_short		default_port,
			    	u_long 		*addr,
				BOOL		use_cur));

Passive Connection Establishment

This function makes a non-blocking accept on a port and polls every second until MAX_ACCEPT_POLL is reached. 
PUBLIC int HTDoAccept PARAMS((HTNetInfo *net));

Caching Hosts Names

This part of the HTTCP module maintains a cache of all visited hosts so that subsequent connects to the same host doesn't imply a new request to the DNS every time.

Multihomed hosts are treated specially in that the time spend on every connect is measured and kept in the cache. On the next request to the same host, the IP-address with the lowest average connect time is chosen. If one IP-address fails completely, e.g. connection refused then it disabled and HTDoConnect tries one of the other IP-addresses to the same host.

If the connect fails in the case of at single-homed host then the entry is removed from the cache and HTDoConnect tries again asking the DNS.

Recalculating the Time-Weights on Multihomed Hosts

On every connect to a multihomed host, the average connect time is updated exponentially for all the entries. 
PUBLIC void HTTCPAddrWeights PARAMS((char * host, time_t deltatime));

Control Variables

This parameter determines the maximum number of hosts in the cache. The default number is 500. 
extern unsigned int	HTConCacheSize;

Errors and status indications

Theese functions return an explanation if an error has occured.

Errno Message

Return error message corresponding to current errno, just like strerror(). 
PUBLIC CONST char * HTErrnoString NOPARAMS;

Description of what Caused the Error

The parameter `where' gives a description of what caused the error, often the name of a system call.

This function should only rarely be called directly. Instead the common error function HTErrorAdd() should be used as then the error is parsed all the way to the user. The function returns a negative status in the unix way. 

PUBLIC int HTInetStatus PARAMS((char * where));

Parse a Cardinal Value

/*	Parse a cardinal value				       parse_cardinal()
**	----------------------
**
** On entry:
** 	*pp points to first character to be interpreted, terminated by
** 	non 0..9 character.
** 	*pstatus points to status already valid,
** 	maxvalue gives the largest allowable value.
**
** On exit:
** 	*pp points to first unread character,
** 	*pstatus points to status updated iff bad
*/

PUBLIC unsigned int HTCardinal PARAMS((int *		pstatus,
				       char **		pp,
				       unsigned int	max_value));

Internet Name Server Functions

The following functions are available to get information about a specified host.

Produce a string for an internet address

This function is equivalent to the BSD system call inet_ntoa in that it converts a numeric 32-bit IP-address to a dotted-notation decimal string. The pointer returned points to static memory which must be copied if it is to be kept. 
PUBLIC CONST char * HTInetString PARAMS((struct sockaddr_in * sin));

Parse an internet node address and port

This function finds the address of a specified host and fills out the sockaddr structure. str points to a string with a node name or number, with optional trailing colon and port number. sin points to the binary internet or decnet address field.

On exit *sin is filled in. If no port is specified in str, that field is left unchanged in *sin. On success, the number of homes on the host is returned. 

PUBLIC int HTParseInet PARAMS((	struct sockaddr_in *	sin,
			       	CONST char *		str,
				BOOL			use_cur));

Name of a Machine on the Other Side of a Socket

This function should have been called HTGetHostByAddr but for historical reasons this is not the case.

Note:This function used to be called HTGetHostName but this is now used to find you own host name, see HTGetHostName() 

PUBLIC char * HTGetHostBySock PARAMS((int soc));

Host address retuned for specified host name

This function gets the address of the host and puts it in to the socket structure. It maintains its own cache of connections so that the communication to the Domain Name Server is minimized. If OK and single homed host then it returns 0 but if it is a multi-homed host then 1 is returned. 
PUBLIC int HTGetHostByName PARAMS((char *host, SockA *sin, BOOL use_cur));

Get Name of This Machine

 This function returns a CONET char pointer to a static location containing the name of this host or NULL if not available. 
PUBLIC CONST char * HTGetHostName NOPARAMS;

Set Name of This Machine

This function overwrites any other value of current host name. This might be set by the user to change the value in the ID value parsed to a news host when posting. The change doesn't influence the Mail Address as they are stored in two different locations. If, however, the change is done before the first call to HTGetMailAddress() then this function will use the new host and domain name. 
PUBLIC void HTSetHostName PARAMS((char * host));

Get Domain Name of This Machine

This function rerturns the domain name part of the host name as returned by HTGetHostName() function. Changing the domain name requires a call to HTSetHostname(). 
PUBLIC CONST char *HTGetDomainName NOPARAMS;

Get User Mail Address

 This functions returns a char pointer to a static location containing the mail address of the current user. The static location is different from the one of the current host name so different values can be assigned. The default value is <USER>@hostname where hostname is as returned by HTGetHostName(). 
PUBLIC CONST char * HTGetMailAddress NOPARAMS;

Set User Mail Address

This function overwrites any other value of current mail address. This might be set by the user to change the value in the From field in the HTTP Protocol. 
PUBLIC void HTSetMailAddress PARAMS((char * address));

#endif   /* HTTCP_H */
End of file