-<!-- $Id: comstack.xml,v 1.2 2001-07-19 23:29:40 adam Exp $ -->
- <chapter><title id="comstack">The COMSTACK Module</title>
+<!-- $Id: comstack.xml,v 1.7 2002-02-24 12:23:43 adam Exp $ -->
+ <chapter id="comstack"><title>The COMSTACK Module</title>
- <sect1><title>Synopsis (blocking mode)</title>
+ <sect1 id="comstack.synopsis"><title>Synopsis (blocking mode)</title>
<programlisting>
-COMSTACK *stack;
+COMSTACK stack;
char *buf = 0;
int size = 0, length_incoming;
char *protocol_package;
int protocol_package_length;
-char server_address[] = "myserver.com:2100";
+char server_address_str[] = "myserver.com:2100";
+void *server_address_ip;
int status;
stack = cs_create(tcpip_type, 1, PROTO_Z3950);
if (!stack) {
- perror("cs_create"); /* note use of perror() here since we have no stack yet */
+ perror("cs_create"); /* use perror() here since we have no stack yet */
exit(1);
}
-status = cs_connect(stack, server_address);
+server_address_ip = cs_addrstr (stack, server_address_str);
+
+status = cs_connect(stack, server_address_ip);
if (status != 0) {
cs_perror(stack, "cs_connect");
exit(1);
if (!length_incoming) {
fprintf(stderr, "Connection closed\n");
exit(1);
-} else if (length_incoming < 0) {
+} else if (length_incoming < 0) {
cs_perror(stack, "cs_get");
exit(1);
}
</programlisting>
</sect1>
- <sect1><title>Introduction</title>
+ <sect1 id="comstack.introduction"><title>Introduction</title>
<para>
The &comstack;
subsystem provides a transparent interface to different types of transport
stacks for the exchange of BER-encoded data. At present, the
- RFC1729 method (BER over TCP/IP), and Peter Furniss' XTImOSI
- stack are supported, but others may be added in time. The philosophy of the
+ RFC1729 method (BER over TCP/IP), and an experimental SSL stack
+ are supported, but others may be added in time. The philosophy of the
module is to provide a simple interface by hiding unused options and
facilities of the underlying libraries. This is always done at the risk
of losing generality, and it may prove that the interface will need
extension later on.
</para>
+ <note>
+ <para>
+ There hasn't been interest in the XTImOSI stack for some years.
+ Therefore, it is no longer supported.
+ </para>
+ </note>
+
<para>
The interface is implemented in such a fashion that only the
sub-layers constructed to the transport methods that you wish to
the interface is still orders of magnitudes more complex than the
transport systems found in many other packages. One reason is that
the interface needs to support the somewhat different requirements of
- the different lower-layer communications stacks; another important reason is
- that the interface seeks to provide a more or less industrial-strength
- approach to asynchronous event-handling. When no function is allowed
- to block, things get more complex - particularly on the server
- side. We urge you to have a look at the demonstration client and server
+ the different lower-layer communications stacks; another important
+ reason is that the interface seeks to provide a more or less
+ industrial-strength approach to asynchronous event-handling.
+ When no function is allowed to block, things get more complex -
+ particularly on the server side.
+ We urge you to have a look at the demonstration client and server
provided with the package. They are meant to be easily readable and
instructive, while still being at least moderately useful.
</para>
</sect1>
- <sect1><title>Common Functions</title>
+ <sect1 id="comstack.common"><title>Common Functions</title>
<sect2><title>Managing Endpoints</title>
<para>
Creates an instance of the protocol stack - a communications endpoint.
- The <literal>type</literal> parameter determines the mode of communication.
+ The <literal>type</literal> parameter determines the mode
+ of communication.
At present, the values
<literal>tcpip_type</literal>
and
- <literal>mosi_type</literal>
+ <literal>ssl_type</literal>
are recognized. The function returns a null-pointer if a system error
- occurs. The <literal>blocking</literal> parameter should be one if you wish
- the association to operate in blocking mode, zero otherwise. The
- <literal>protocol</literal> field should be one of
- <literal>PROTO_SR</literal> or <literal>PROTO_Z3950</literal>.
+ occurs. The <literal>blocking</literal> parameter should be one if
+ you wish the association to operate in blocking mode, zero otherwise.
+ The <literal>protocol</literal> field should be
+ <literal>PROTO_Z3950</literal>.
+ Protocol <literal>PROTO_SR</literal> is no longer supported.
</para>
-
<synopsis>
int cs_close(COMSTACK handle);
</synopsis>
<para>
Closes the connection (as elegantly as the lower layers will permit),
- and releases the resouces pointed to by the
+ and releases the resources pointed to by the
<literal>handle</literal>
parameter. The
<literal>handle</literal>
The <function>cs_get()</function> 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 callig <function>cs_get()</function>, and before
+ by the subsystem. After calling <function>cs_get()</function>, and before
waiting for more input, You should always call
<function>cs_more()</function>
to check if there's a full protocol package already read. If
<variablelist>
<varlistentry><term>CS_NONE</term><listitem><para>
- No event is pending. The data found on the line was not a complete package.
+ No event is pending. The data found on the line was not a
+ complete package.
</para></listitem></varlistentry>
<varlistentry><term>CS_CONNECT</term><listitem><para>
<varlistentry><term>CS_DISCON</term><listitem><para>
The other side has closed the connection (or maybe sent a disconnect
request - but do we care? Maybe later). Call
- <function>cs_close</function> to close your end of the association as well.
+ <function>cs_close</function> to close your end of the association
+ as well.
</para></listitem></varlistentry>
<varlistentry><term>CS_LISTEN</term><listitem><para>
- A connect request has been received. Call <function>cs_listen</function>
- to process the event.
+ A connect request has been received.
+ Call <function>cs_listen</function> to process the event.
</para></listitem></varlistentry>
<varlistentry><term>CS_DATA</term><listitem><para>
- There's data to be found on the line. Call <function>cs_get</function>
- to get it.
+ There's data to be found on the line.
+ Call <function>cs_get</function> to get it.
</para></listitem></varlistentry>
</variablelist>
</sect1>
- <sect1><title>Client Side</title>
+ <sect1 id="comstack.client"><title>Client Side</title>
<synopsis>
int cs_connect(COMSTACK handle, void *address);
<para>
Complete a connect operation initiated by <function>cs_connect()</function>.
It will return 0 on success; 1 if the operation has not yet completed (in
- this case, call the function again later); -1 if an error has occured.
+ this case, call the function again later); -1 if an error has occurred.
</para>
</sect1>
- <sect1><title>Server Side</title>
+ <sect1 id="comstack.server"><title>Server Side</title>
<para>
- To establish a server under the <application>inetd</application> server, you
- can use
+ To establish a server under the <application>inetd</application>
+ server, you can use
</para>
<synopsis>
COMSTACK cs_createbysocket(int socket, CS_TYPE type, int blocking,
- int protocol);
+ int protocol);
</synopsis>
<para>
</synopsis>
<para>
- This finalises the server-side association establishment, after
+ This finalizes the server-side association establishment, after
cs_listen has completed successfully. It returns a new connection
endpoint, which represents the new association. The application will
typically wish to fork off a process to handle the association at this
</synopsis>
<para>
- on an established connection to retrieve the hostname of the remote host.
+ on an established connection to retrieve the host-name of the remote host.
</para>
<note>
</note>
</sect1>
- <sect1><title>Addresses</title>
+ <sect1 id="comstack.addresses"><title>Addresses</title>
<para>
The low-level format of the addresses are different depending on the
</para>
<synopsis>
- struct sockaddr_in *tcpip_strtoaddr(char *str);
-
- struct netbuf *mosi_strtoaddr(char *str);
+ void *cs_straddr(COMSTACK handle, const char *str);
</synopsis>
<para>
</synopsis>
<para>
- The <literal>hostname</literal> can be either a domain name or an IP address.
- The port number, if omitted, defaults to 210.
+ The <literal>hostname</literal> can be either a domain name or an
+ IP address. The port number, if omitted, defaults to 210.
</para>
<para>
- For OSI, the format is
+ In all transport modes, the special hostname "@" is mapped
+ to any local address (the manifest constant <literal>INADDR_ANY</literal>).
+ It is used to establish local listening endpoints in the server role.
</para>
- <synopsis>
- [ <t-selector> '/' ] <host> [ ':' <port> ]
- </synopsis>
-
<para>
- The transport selector is given as an even number of hex digits.
+ When a connection has been established, you can use
</para>
- <para>
- You'll note that the address format for the OSI mode are just a subset
- of full presentation addresses. We use presentation addresses because
- xtimosi doesn't, in itself, allow access to the X.500 Directory
- service. We use a limited form, because we haven't yet come across an
- implementation that used more of the elements of a full p-address. It
- is a fairly simple matter to add the rest of the elements to the
- address format as needed, however: Xtimosi <emphasis>does</emphasis>
- support the full P-address structure.
- </para>
+ <synopsis>
+ char *cs_addrstr(COMSTACK h);
+ </synopsis>
<para>
- In both transport modes, the special hostname "@" is mapped
- to any local address (the manifest constant <literal>INADDR_ANY</literal>).
- It is used to establish local listening endpoints in the server role.
+ to retrieve the host name of the peer system. The function returns
+ a pointer to a static area, which is overwritten on the next call
+ to the function.
</para>
<para>
- When a connection has been established, you can use
+ A fairly recent addition to the &comstack; module is the utility
+ function
</para>
-
<synopsis>
- char cs_addrstr(COMSTACK h);
+ COMSTACK cs_create_host (const char *str, int blocking, void **vp);
</synopsis>
-
<para>
- to retrieve the host name of the peer system. The function returns a pointer
- to a static area, which is overwritten on the next call to the function.
+ which is just a wrapper around <function>cs_create</function> and
+ <function>cs_straddr</function>. The <parameter>str</parameter>
+ is similar to that described for <function>cs_straddr</function>
+ but with a prefix denoting the &comstack; type. Prefixes supported
+ are <literal>tcp:</literal> and <literal>ssl:</literal> for
+ TCP/IP and SSL respectively. If no prefix is given, then TCP/IP
+ is used. The <parameter>blocking</parameter> is passed to
+ function <function>cs_create</function>. The third parameter
+ <parameter>vp</parameter> is a pointer to &comstack; stack type
+ specific values.
+ For SSL (ssl_type) <parameter>vp</parameter> is an already create
+ OpenSSL CTX. For TCP/IP <parameter>vp</parameter> is unused (can be
+ set to <literal>NULL</literal>.
</para>
- <note>
- <para>
- We have left the issue of X.500 name-to-address mapping open, for the
- moment. It would be a simple matter to provide a table-based mapping,
- if desired. Alternately, we could use the X.500 client-function that
- is provided with the ISODE (although this would defeat some of the
- purpose of using ThinOSI in the first place. We have been told that it
- should be within the realm of the possible to implement a lightweight
- implementation of the necessary X.500 client capabilities on top of
- ThinOSI. This would be the ideal solution, we feel. On the other hand, it
- still remains to be seen just what role the Directory will play in a world
- populated by ThinOSI and other pragmatic solutions.
- </para>
- </note>
-
</sect1>
- <sect1><title>Diagnostics</title>
+ <sect1 id="comstack.diagnostics"><title>Diagnostics</title>
<para>
All functions return -1 if an error occurs. Typically, the functions
provided.
</para>
</sect1>
-
- <sect1><title>Enabling OSI Communication</title>
-
- <sect2><title>Installing Xtimosi</title>
- <para>
- Although you will have to download Peter Furniss' XTI/mOSI
- implementation for yourself, we've tried to make the integration as
- simple as possible.
- </para>
-
- <para>
- The latest version of xtimosi will generally be under
- </para>
-
- <screen>
- ftp://pluto.ulcc.ac.uk/ulcc/thinosi/xtimosi/
- </screen>
-
- <para>
- When you have downloaded and unpacked the archive, it will (we assume)
- have created a directory called <literal>xtimosi</literal>.
- We suggest that you place this directory <emphasis>in the same
- directory</emphasis> where you unpacked the &yaz;
- distribution. This way, you shouldn't have to fiddle with the
- makefiles of &yaz; beyond uncommenting a few lines.
- </para>
-
- <para>
- Go to <literal>xtimosi/src</literal>, and type "make libmosi.a/".
- This should generally create the library, ready to use.
- </para>
-
- <note>
- <para>
- The currently available release of xtimosi has some inherent
- problems that make it disfunction on certain platforms - eg. the
- Digital OSF/1 workstations. It is supposedly primarily a
- compiler problem, and we hope to see a release that is generally
- portable. While we can't guarantee that it can be brought to work
- on your platform, we'll be happy to talk to you about problems
- that you might see, and relay information to the author of the
- software. There are some signs that the <application>gcc</application>
- compiler is more likely to produce a fully functional library, but this
- hasn't been verified (we think that the problem is limited to the use
- of hexadecimal escape-codes used in strings, which are silently
- ignored by some compilers).
- </para>
- <para>
- A problem has been encountered in the communication with
- ISODE-based applications. If the ISODE presentation-user calls
- <function>PReadRequest()</function> with a timeout value different
- from <literal>OK</literal> or <literal>NOTOK</literal>,
- he will get an immediate TIMEOUT abort when receiving large (>2041
- bytes, which is the SPDU-size that the ISODE likes to work with) packages
- from an xtimosi-based implementation (probably most
- other implementations as well, in fact). It seems to be a flaw in the
- ISODE API, and the workaround (for ISODE users) is to either not
- use an explicit timeout (switching to either blocking or
- nonblocking mode), or to check that the timer really has expired
- before closing the connection.
- </para>
- </note>
-
- <para>
- The next step in the installation is to modify the makefile in the toplevel
- &yaz;
- directory. The place to change is in the top of the file, and is
- clearly marked with a comment.
- </para>
-
- <para>
- Now run <literal>make</literal> in the &yaz; toplevel directory (do a
- <literal>make clean</literal> first, if the system has been previously
- made without OSI support). Use the &yaz;
- <application>yaz-ztest</application> and <application>yaz-client</application>
- demo programs to verify that OSI communication works OK. Then, you can go
- ahead and try to talk to other implementations.
- </para>
-
- <note>
- <para>
- Our interoperability experience is limited to version
- 7 of the Nordic SR-Nett package, which has had several
- protocol errors fixed from the earlier releases. If you have
- problems or successes in interoperating with other
- implementations, we'd be glad to hear about it, or to help
- you make things work, as our resources allow.
- </para>
- </note>
-
- <para>
- If you write your own applications based on &yaz;, and you wish to
- include OSI support, the procedure is equally simple. You should
- include the <filename>xmosi.h</filename> header file in addition to
- <filename>comstack.h</filename>. <filename>xmosi.h</filename>
- will define the manifest constant <literal>mosi_type</literal>, which you
- should pass to the <function>cs_create()</function> function. In
- addition, you should use the function <function>mosi_strtoaddr()</function>
- rather than <function>tcpip_strtoaddr()</function> when you need to
- prepare an address.
- </para>
-
- <para>
- When you link your application, you should include (after the
- <filename>libyaz.a</filename> library) the <literal>libmosi.a</literal>
- library, and the <filename>librfc.a</filename> library provided with
- &yaz; (for OSI transport).
- </para>
- <para>
- As always, it can be very useful, if not essential, to have a look at the
- example applications to see how things are done.
- </para>
-
- </sect2>
- <sect2><title>OSI Transport</title>
-
- <para>
- Xtimosi requires an implementation of the OSI transport service under
- the X/OPEN XTI API. We provide an implementation of the RFC1006
- encapsulation of OSI/TP0 in TCP/IP (through the Berkeley Sockets API),
- as an independent part of &yaz; (it's found under the
- <filename>rfc1006</filename> directory).
- If you have access to an OSI transport provider under XTI,
- you should be able to make that work too, although it may require
- tinkering with the <function>mosi_strtoaddr()</function> function.
- </para>
- </sect2>
-
- <sect2><title>Presentation Context Management</title>
-
- <para>
- To simplify the implementation, we use Peter Furniss' alternative (PRF)
- option format
- for the Control of the presentation negotiation phase. This format
- is enabled by default when you
- compile xtimosi.
- </para>
-
- <para>
- The current version of &yaz; does <emphasis>not</emphasis> support
- presentation-layer negotiation of response record formats. The primary
- reason is that we have had access to no other SR or Z39.50
- implementations over OSI that used this
- method. Secondarily, we believe that the EXPLAIN facility is a superior
- mechanism for relaying target capabilities in this respect. This is not to
- say that we have no intentions of supporting presentation context
- negotiation - we have just hitherto given it a lower priority than other
- aspects of the protocol.
- </para>
- <para>
- One thing is certain: The addition of this capability to &yaz; should
- have only a minimal impact on existing applications, and on the
- interface to the software in general. Most likely, we will add an extra
- layer of interface to the processing of EXPLAIN records, which will
- convert back and forth between <literal>oident</literal> records (see
- section <link linkend="oid">Object Identifiers</link>) and direct or
- indirect references, given the current association setup. Implementations
- based on any of the higher-level interfaces will most likely not have to
- be changed at all.
- </para>
- </sect2>
- </sect1>
- <sect1><title>Summary and Synopsis</title>
+ <sect1 id="comstack.summary"><title>Summary and Synopsis</title>
<synopsis>
#include <comstack.h>
- #include <tcpip.h> /* this is for TCP/IP support */
- #include <xmosi.h> /* and this is for mOSI support */
+ #include <tcpip.h> /* this is for TCP/IP and SSL support */
COMSTACK cs_create(CS_TYPE type, int blocking, int protocol);
COMSTACK cs_createbysocket(int s, CS_TYPE type, int blocking,
int protocol);
+ COMSTACK cs_create_host (const char *str, int blocking,
+ void **vp);
int cs_bind(COMSTACK handle, int mode);
int cs_look(COMSTACK handle);
- struct sockaddr_in *tcpip_strtoaddr(char *str);
+ void *cs_straddr(COMSTACK handle, const char *str);
- struct netbuf *mosi_strtoaddr(char *str);
+ char *cs_addrstr(COMSTACK h);
extern int cs_errno;
sgml-indent-step:1
sgml-indent-data:t
sgml-parent-document: "yaz.xml"
- sgml-local-catalogs: "../../docbook/docbook.cat"
+ sgml-local-catalogs: nil
sgml-namecase-general:t
End:
-->
projects / yaz-moved-to-github.git / blobdiff