FAQ version 1.1.0

Last updated: 18^th August 1998

Copyright

This FAQ was written by Richard Dawe. Please see his details for more information.

Table Of Contents

• Question 1.1: What is libsocket?
• Question 1.2: Who wrote libsocket?
• Question 1.3: Which versions of libsocket does this FAQ cover?
• Question 1.4: I have a question that is not covered in the FAQ. What should I do?

Section 2: Operating System Support

• Question 2.1: Will libsocket work with DOS?
• Question 2.2: Will libsocket work with Windows 3.x?
• Question 2.3: Will libsocket work with Windows '95?
• Question 2.4: Will libsocket work with Windows '98?
• Question 2.5: Will libsocket work with Windows NT?
• Question 2.6: Will libsocket work with Linux?

Section 3: Installation and Compilation

• Question 3.1: How should I rebuild libsocket?
• Question 3.2: When I do "make installman", the man pages are installed into the wrong place. Why?
• Question 3.3: make complains that I don't have rm. Why?
• Question 3.4: How do I compile a debugging version of the library?
• Question 3.5: I don't like your global Makefile settings. How do I change them?
• Question 3.6: Your library sucks. How do I uninstall it?

Section 4: Configuration

• Question 4.1: How can I find out my computer's IP address?
• Question 4.2: How can I find out the DNS servers' IP addresses on my network?
• Question 4.3: I've run netsetup, but my libsocket programs don't use the new settings. Why?
• Question 4.4: I use a dial-up link and my IP address keeps changing. How should I configure libsocket?
• Question 4.5: My computer is on a LAN, but I use DHCP and my IP address keeps changing. How should I configure libsocket?

Section 5: Execution

• Question 5.1: Why does my program using libsocket crash?
• Question 5.2: Why can't my program using libsocket create sockets?
• Question 5.3: Why does my program using libsocket stop working?

Section 6: Programming with libsocket

• Question 6.1: Can I use libsocket with multithreading libraries?
• Question 6.2: Are there any Remote Procedure Call (RPC) libraries for libsocket?
• Question 6.3: I want to port a Unix program to libsocket. What transport protocols, etc. does it support?
• Question 6.4: Why does gcc complain of parse errors when I use ioctl()?
• Question 6.5: When I use perror() or strerror(), I don't get a meaningful error message for some errors. Why?

Section 7: Miscellaneous Questions

• Question 7.1: How do I find out if I have Winsock 2?
• Question 7.2: How can I uninstall Winsock 2?
• Question 7.3: How can I install Winsock 2?

Section 8: Socket Programming Information

Section 9: Other Networking Libraries

Section 1: Introduction

Question 1.1: What is libsocket?

BSD sockets are the standard way of programming networking on Unix. BSD sockets are also available in a modified form on Windows platforms in the form of Winsock, which has many common functions. In short, if you're used to programming with sockets on Unix, then moving to libsocket should be a relatively pain-free transition.

libsocket uses a backdoor that Windows provides to DOS programs to use Windows's networking. This backdoor is the Winsock device driver, WSOCK.386 or WSOCK.VXD.

libsocket also incorporates some source code from Linux, namely the resolver. This resolves names of the "foo.bar.com" to IP addresses like 192.168.0.123.

Question 1.2: Who wrote libsocket?

The registry code was written by the Regdos Group.

For contributions, please see the credits, or the relevant section in the libsocket manual page (use "man libsocket").

Question 1.3: Which versions of libsocket does this FAQ cover?

Unless the version of libsocket is mentioned, it is not relevant to the question. In other words, all versions of libsocket are covered.

Question 1.4: I have a question that is not covered in the FAQ. What should I do?

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Section 2: Operating System Support

Question 2.1: Will libsocket work with DOS?

Question 2.2: Will libsocket work with Windows 3.x?

Question 2.3: Will libsocket work with Windows '95?

Windows '95 is the platform that libsocket has been written on, and is hence the most tested. I have only used it on Windows '95 with Service Pack 1 installed - this is the original version. I do not know whether it works with Operating System Releases 2 or 2.1 (OSR2 and OSR2.1), but it should do.

Question 2.4: Will libsocket work with Windows '98?

Question 2.5: Will libsocket work with Windows NT?

libsocket will not work under Windows NT and probably never will. Windows NT is much more securely designed, so the backdoors libsocket uses to access Winsock under Windows '95 simply aren't there. As with long filenames for DOS programs in Windows NT DOS boxes, this is unlikely to change.

[Later: It looks like a driver to allow LFN access in NT DOS boxes has emerged now. However, it's still unlikely that libsocket will ever work under NT.]

Question 2.6: Will libsocket work with Linux?

libsocket shouldn't work with Linux, but should compile under it. After all, DJGPP is a port of the GNU C compiler to DOS.

Section 3: Installation and Compilation

Question 3.1: How should I rebuild libsocket?

    make distclean
    make dep
    make all
    make install

If you wish to compile using long filenames, then use "make lfn" too. If you haven't installed the man pages, you might like to "make installman" too. If you'd like to rebuild the HTML versions of the man pages, use "make htmldocs" (this will take a few minutes & requires the source distribution).

To completely rebuild libsocket, you will need the standard set of ZIPs required to compile C programs, the GNU Fileutils (see question 3.3), man (from man12b.zip) and Perl (from perl54b.zip, or ActiveState's Perl for Win32). If you do not wish to rebuild the HTML versions of the man pages, man and Perl are not required.

Question 3.2: When I do "make installman", the man pages are installed into the wrong place. Why?

Question 3.3: make complains that I don't have rm. Why?

Question 3.4: How do I compile a debugging version of the library?

First of all, you will need the source distribution. After that, it depends which version of the library you have:

• Version 0.7.1 & later has Makefile targets to configure for debugging. Use "make debug" to generate a Makefile.cfg with debugging from the template file Make-cfg.in. Use "make nodebug" to turn this off. After generating Makefile.cfg with either of these options, rebuild the library using the procedure in question 3.1. Note that the Makefile.cfg built with "make debug" passes the options "-g" and "-DDEBUG" to gcc, i.e. the constant DEBUG is #define'd.

• Version 0.7.0 & earlier needs Makefile.cfg to edited, and the option "-g" to the "CFLAGS" line. Then rebuild the library as described in question 3.1. If you add the option "-DDEBUG" to the "CFLAGS" line, then the source will fail to compile without editing. This can be fixed by editing the file r_opts.h, or res_options.h, depending on the version, and wrapping it's #define of DEBUG in an #ifndef ... #endif, like so:

	#ifndef DEBUG
	#define DEBUG
	#endif

Question 3.5: I don't like your global Makefile settings. How do I change them?

This depends on which version of the library you have:

• Version 0.7.1 & later has a template global settings Makefile called Make-cfg.in, which should be edited to your requirements. Then use "make debug" or "make nodebug" to create the global settings Makefile, Makefile.cfg, with your settings.

• Version 0.7.0 & earlier needs Makefile.cfg to be edited directly.

Question 3.6: Your library sucks. How do I uninstall it?

If you haven't used the Makefile target "install" then no action is required. Otherwise, it depends on which version of the library you have:

• Version 0.7.3 (& later) has a Makefile target called "uninstall". Use "make uninstall" to uninstall, or look at its actions if you'd rather do it manually.

• Version 0.7.2 & earlier require manual uninstallation. The files to remove from the DJGPP directory are:

  • include/netdb.h
  • include/winsock.h
  • include/ws.h
  • include/sys/socket.h
  • include/arpa/inet.h
  • lib/libsocke.a or lib/libsocket.a

Section 4: Configuration

Question 4.1: How can I find out my computer's IP address?

Question 4.2: How can I find out the DNS servers' IP addresses on my network?

Question 4.3: I've run netsetup, but my libsocket programs don't use the new settings. Why?

netsetup creates the files hosts.eg, networks.eg, host.conf and resolv.conf in the setup/ directory. These have to be copied to the libsocket settings directory. If you've set the LIBSOCKET environment variable to point to a directory, then copy them there. Otherwise they should be copied to the Windows directory (back up the current hosts and networks files!). Remember to edit hosts.eg and networks.eg, if necessary, and rename them to hosts and networks.

Question 4.4: I use a dial-up link and my IP address keeps changing. How should I configure libsocket?

Question 4.5: My computer is on a LAN, but I use DHCP and my IP address keeps changing. How should I configure libsocket?

Both these connections use DHCP, which stands for Dynamic Host Configuration Protocol. This allocates IP addresses dynamically and allows them to be managed and assigned from a central point. It also allows other sorts of information to given out, like DNS IP addresses. Thus, if a DNS IP address is changed using DHCP, no manual reconfiguration of all the client computers is necessary.

The problem is thus: libsocket has no way of obtaining the IP addresses in its auto-configuration, so it has to be told. But how do you know the IP addresses? Here's the solution (fudge?):

• For the computer's IP address, use 127.0.0.1, the loopback address. This will always work. You should see two lines in the hosts file, generated by netsetup, like so:

  127.0.0.1	localhost
  127.0.0.1	mycomputername
  

• The DNS IP address is trickier. This is not really a solution, but it will probably work for a while. Log in a few times and note the DNS IP address as given by 'winipcfg' (see question 4.1 and question 4.2). Then use this DNS IP address when you run netsetup. This technique will work until the DNS IP address changes, which may or may not be infrequently.

Section 5: Execution

Question 5.1: Why does my program using libsocket crash?

Question 5.2: Why can't my program using libsocket create sockets?

Question 5.3: Why does my program using libsocket stop working?

If you have killed your program by closing the command prompt it is running in, and then run the program in a new command prompt, then the program may hang or fail to bind to sockets with error 98. It seems that killing libsocket programs between one and four times leads to this problem. The only solution appears to be to restart Windows, i.e. in order to re-initialise WSOCK.VXD.

Section 6: Programming with libsocket

Question 6.1: Can I use libsocket with multithreading libraries?

I looked at two multithreading libraries for DJGPP, found in the v2tk/ directory of the DJGPP archive: jtlwp20 and pwdlwp03. The second library is based on (an earlier version of?) the first.

With jtlwp20, there appear to be two ways of stopping the libsocket functions being called multiply. The first method is to call lwpCreateMutex() for all the libsocket functions you use. The second method is to use place lwpEnterCriticalSection() and lwpLeaveCriticalSection() around the code that uses libsocket functions.

With pwdlwp03, one has to create a semaphore using lwp_init_semaphore(), then wait for it to become free before using libsocket calls using lwp_wait_semaphore() and then release it when one's finished using lwp_release_semaphore().

Please see the multithreading libraries' documentation for more details.

While libsocket's code may be non-reentrant, I don't think this totally ruins multithreading programs. I think it would still be possible to write a Web server that runs well in spite of the limitations.

Question 6.2: Are there any Remote Procedure Call (RPC) libraries for libsocket?

Question 6.3: I want to port a Unix program to libsocket. What transport protocols, etc. does it support?

Question 6.4: Why does gcc complain of parse errors when I use ioctl()?

DJGPP includes definitions for ioctl()'s parameters in the include file sys/io.h. However, they will not be defined if you include sys/io.h, as they are enclosed in an '#if 0 ... #endif' pair. There are three possible solutions to this problem:

• Edit sys/io.h so it says '#if 1' instead of '#if 0'. I do not recommend this as it may break the compilation of many things - it certainly stops libsocket from compiling. Besides, editing DJGPP's standard include files has got to be a bad idea.

• Use the include file winsock.h, included with libsocket, which defines what you need.

• Wait for the next version of DJGPP, which will probably have better support for ioctl() (see DJGPP's File System Extensions, FSEXT). This isn't very helpful.

This problem affects the compilation of programs that use non-blocking sockets, i.e. the FIONBIO parameter for ioctl(). I would recommend including winsock.h to circumvent this problem.

Question 6.5: When I use perror() or strerror(), I don't get a meaningful error message for some errors. Why?

DJGPP's C library, libc, doesn't come with all the Unix error messages built in, so when you use perror() or strerror() with socket errors, no error message is known. libsocket provides the functions lsck_perror() and lsck_strerror(), which work the same way, to provide these error messages. If the error isn't a socket error, then it is passed to the libc perror() and strerror() functions. So, the solution is to replace occurrences of perror() with lsck_perror() and strerror() with lsck_strerror(), until libc contains all the error messages needed.

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Section 7: Miscellaneous Questions

Question 7.1: How do I find out if I have Winsock 2?

Question 7.2: How can I uninstall Winsock 2?

It might not be possible to uninstall it, e.g. in the case of Windows '98. If the operating system originally came with Winsock 1.1 then it is possible. Some programs such as Sun's Java Software Development Kit (JDK) 1.1.5 install Winsock 2 for you.

Question 7.3: How can I install Winsock 2?

The simplest way of doing this is to obtain the Winsock 2 SDK for Windows '95 from Microsoft's web site. This includes an install program that will install Winsock 2 and create the back-up described above. I know this works as I've been through the install-uninstall cycle several times.

Section 8: Socket Programming Information

This section has been moved to the libsocket links page.

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Section 9: Other Networking Libraries

This section has been moved to the libsocket links page.

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The layout of this page is by Indrek Mandre, and the content is by Richard Dawe.