COMSTACK cs_create(CS_TYPE type, int blocking, int protocol);
Creates an instance of the protocol stack - a communications endpoint.
type parameter determines the mode
of communication. At present the following values are supported:
TCP/IP (BER over TCP/IP or HTTP over TCP/IP)
Secure Socket Layer (SSL). This COMSTACK is experimental and is not fully implemented. If HTTP is used, this effectively is HTTPS.
Unix socket (unix only). Local Transfer via file socket. See unix(7).
cs_create function returns a null-pointer
if a system error occurs.
blocking parameter should be '1' if
you wish the association to operate in blocking mode, and '0' otherwise.
protocol field should be
PROTO_SR is no longer supported.
void cs_close(COMSTACK handle);
Closes the connection (as elegantly as the lower layers will permit),
and releases the resources pointed to by the
should not be referenced again after this call.
We really need a soft disconnect, don't we?
int cs_put(COMSTACK handle, char *buf, int len);
buf down the wire.
In blocking mode, this function will return only when a full buffer has
been written, or an error has occurred. In nonblocking mode, it's
possible that the function will be unable to send the full buffer
at once, which will be indicated by a return value of 1.
The function will keep track of the number of octets already written; you
should call it repeatedly with the same values of
len, until the buffer has been transmitted.
When a full buffer has been sent, the function will return 0 for
success. The return value -1 indicates an error condition (see below).
int cs_get(COMSTACK handle, char **buf, int *size);
Receives a PDU or HTTP Response from the peer. Returns the number of
In nonblocking mode, it is possible that not all of the packet can be
read at once. In this case, the function returns 1. To simplify the
interface, the function is
responsible for managing the size of the buffer. It will be reallocated
if necessary to contain large packages, and will sometimes be moved
around internally by the subsystem when partial packages are read. Before
for the first time, the buffer can be initialized to the null pointer,
and the length should also be set to 0 (cs_get will perform a
on the buffer for you). When a full buffer has been read, the size of
the package is returned (which will always be greater than 1).
The return value -1 indicates an error condition.
See also the
cs_more() function below.
int cs_more(COMSTACK handle);
cs_more() function should be used in conjunction
cs_get() function will sometimes
(notably in the TCP/IP mode) read more than a single protocol package
off the network. When this happens, the extra package is stored
by the subsystem. After calling
cs_get(), and before
waiting for more input, You should always call
to check if there's a full protocol package already read. If
can be used to immediately fetch the new package. For the
subsystem, the function should always return 0, but if you want your
stuff to be protocol independent, you should use it.
function is required because the RFC1729-method
does not provide a way of separating individual PDUs, short of
partially decoding the BER. Some other implementations will carefully
nibble at the packet by calling
several times. This was felt to be too inefficient (or at least
clumsy) - hence the call for this extra function.
int cs_look(COMSTACK handle);
This function is useful when you're operating in nonblocking
mode. Call it when
tells you there's something happening on the line. It returns one of
the following values:
No event is pending. The data found on the line was not a complete package.
A response to your connect request has been received. Call
to process the event and to finalize the connection establishment.
The other side has closed the connection (or maybe sent a disconnect
request - but do we care? Maybe later). Call
cs_close to close your end of the association
A connect request has been received.
cs_listen to process the event.
There's data to be found on the line.
cs_get to get it.
You should be aware that even if
tells you that there's an event event pending, the corresponding
function may still return and tell you there was nothing to be found.
This means that only part of a package was available for reading. The
same event will show up again, when more data has arrived.
int cs_fileno(COMSTACK h);
returns the file descriptor of the association. Use this when
file-level operations on the endpoint are required
select(2) operations, specifically).