Welcome to The Winsock Programmer's FAQ

This is the Winsock Programmer's FAQ, the current reincarnation of the original Winsock FAQ by Mark Towfiq et al. This FAQ's maintainer is Warren Young. The main FAQ site and its mirrors are listed in the Introduction section.

This FAQ will try to answer the most commonly-asked questions on the alt.winsock.programming and comp.os.ms-windows.programmer.tools.winsock newsgroups. The FAQ is also growing into a repository of Winsock programming information for all levels of programmers. Please email me if you have any corrections or additions for the list.

If you would like to view this FAQ off-line, you can download a ZIPped version (240K, last packaged 1999.06.27) of these pages.

What's New?

• 1999.08.30 - Updated the ICMP Ping Example so that it compiles cleaner, and updated the commentary to note that the program still works on Microsoft's newest platforms (Win98 and Win2K) despite their past threats to remove the API.

  Added some new info on the "how many sockets can you have open" problem discussed in Question 3.16. The new info discloses kernel internals that limit the number of sockets you can create on Windows NT 4.0 and Windows 2000. The item also includes some empirical data I've collected from Internet postings; some conclusions are drawn based on this data and the known kernel algorithms. I also added some info on increasing the low hard limit imposed under Win9x.

  Improved the accuracy of the info on waitable timers in Question 2.14.

  Added the Search function, courtesy of FreeFind.

  Added Question 2.18, regarding the Winsock link library. (This question comes up with distressing frequency, so I broke down and added it to the FAQ. What is the world coming to? :-/)

  Previous "What's New" Entries...

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Contents

0.1 - The Original Introduction
0.2 - A Bit About the Maintainer
0.3 - Legal Stuff
0.4 - Mirrors
0.5 - What if your question is not in the FAQ?
0.6 - Language Bias
0.7 - Acknowledgements

1.1 - What is Winsock?
1.2 - What is the latest version?
1.3 - When is the next rev of the specification?
1.4 - Where can I get a Winsock implementation?
1.5 - Why isn't there just one Winsock DLL? Do I need a network stack to use it?
1.6 - Is there a version of Winsock for { OS/2, DOS, Unix, etc. }?
1.7 - Can Winsock speak { DECNet, IPX/SPX, etc. }?
1.8 - What does Winsock 2 have that Winsock 1.1 doesn't?
1.9 - Where can I get Winsock 2?

2.1 - Are there any sample apps on the Net?
2.2 - How do I speak { HTTP, POP3, SMTP, FTP, Telnet, NNTP, etc. } with Winsock?
2.3 - How do I get my IP address from within a Winsock program?
2.4 - What kind of socket should I use?
2.5 - Do I need to initialize the WSAData structure before calling WSAStartup?
2.6 - If I write a Winsock program, will I be able to communicate with a Unix Sockets program?
2.7 - Can I use Winsock with { Delphi, Visual Basic, Visual COBOL, etc. }?
2.8 - How do I detect when my TCP connection is closed?
2.9 - Are there any tools available for debugging Winsock programs?
2.10 - How do I get a readable error message from a Winsock error number?
2.11 - Winsock keeps returning the error WSAEWOULDBLOCK. What's wrong with my program?
2.12 - What's the proper way to close a TCP socket?
2.13 - What can you tell me about MFC's CSocket and CAsyncSocket?
2.14 - How can I change the timeout for a Winsock function?
2.15 - How do I send a broadcast packet?
2.16 - How do I detect an abnormal network disconnect?
2.17 - I'm writing a server. What's a good network port to use?
2.18 - I'm getting link errors when compiling Winsock programs. What's wrong?

3.1 - How can I open a raw data socket?
3.2 - How can I "ping" another machine with Winsock?
3.3 - How do I share a socket between two processes?
3.4 - How can I get access to the {route, ARP, interface, etc.} table?
3.5 - How can I get the local username?
3.6 - Is it possible to create sockets that map to a DLL rather than an application?
3.7 - I'm having trouble porting a BSD sockets program to Winsock. Help!
3.8 - How do I get the MAC (a.k.a. hardware) address of the local Ethernet adapter?
3.9 - In a multithreaded application, can more than one thread access a single socket?
3.10 - If two threads in an application call recv() on a socket, will they each get the same data?
3.11 - Is there any way for two threads to be notified when something happens on a socket?
3.12 - How do I detect if the modem is connected?
3.13 - How can I capture packets on a LAN with Winsock?
3.14 - How can I change the IP or TCP header of a packet?
3.15 - When should I turn off the Nagle algorithm?
3.16 - How many simultaneous sockets can I have open with Winsock?
3.17 - Can I change FD_SETSIZE to make select() wait on more than 64 sockets?
3.18 - How do I make Winsock use a specific network interface to make a connection?
3.19 - How do I write my program to work through a firewall?
3.20 - Is it a bad idea to bind() to a particular port in a client program?
3.21 - What is the { SYN, ACK, FIN, RST } bit?

4.1 - Winsock Libraries and Controls
4.2 - Sample Winsock Applications and Tutorials
4.3 - Web Pages
4.4 - Winsock SDKs and Specifications
4.5 - Winsock Debugging Tools
4.6 - Network Suite Vendors
4.7 - Miscellaneous

Section 5 - Examples

Example 1 - Getting the Local IP Address
Example 2 - Pinging a Host Using Microsoft's ICMP.DLL
Example 3 - Pinging a Host Using Raw Sockets
Example 4 - How to Get the Local User Name
Example 5 - How to Pass a Socket Handle in Win32
Example 6 - How to Get the MAC (a.k.a. "hardware") Address, NetBIOS method
Example 7 - How to Get the MAC (a.k.a. "hardware") Address, RPC method
Example 8 - Getting the Network Interface List
Example 9 - Finding the Maximum Number of Open Sockets
Example 10 - Several Basic Winsock Programs

Section 6 - Tutorials

Tutorial 1 - What Kind of Socket Should I Use?
Tutorial 2 - Winsock for the Impatient
Tutorial 3 - Winsock's Compatibility With BSD Sockets
Tutorial 4 - How to Use TCP Effectively
Tutorial 5 - Debugging TCP
Tutorial 6 - The Lame List

Section 7 - Reviews

Books

Win32 Network Programming by Ralph Davis
WinSock 2.0 by Lewis Napper
Windows Sockets Network Programming by Bob Quinn and Dave Shute
TCP/IP Illustrated, volume 1 by W. Richard Stevens
Unix Network Programming, volume 1 by W. Richard Stevens


Software


Nothing yet!

Section 8 - Glossary

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Please send updates and corrections to <tangent@cyberport.com>.