This is the Winsock Programmer's FAQ. See the Introduction section for history, a list of mirrors, and information about the maintainer.

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 (278K, last packaged 2000.04.29) of these pages.

What's New?

2000.04.25

Added info to the item about detecting abnormal disconnects warning against using keepalives to detect these sorts of problems.

2000.04.24

Fixed several "point-0" problems. (Yes, FAQs have them, too!)

2000.04.23

Finished the redesign. This also marks the first FAQ announcement in several months.

Added the review of Jones and Ohlund's Network Programming for Microsoft Windows.

Added an article by Tom Sanfilippo that shows how to use the undocumented WsControl() function. This function is used by Windows 95's winipcfg program to view and change various IP parameters. There is no documented way to get at a lot of this info, so this article is very welcome! Thanks, Tom!

(I didn't plan it, but this "FAQ rebirth" occurred on Easter Sunday. Apropriate, no?)

2000.03.26

Today I began a total revamp of the FAQ's look, content and organization. Virtually every FAQ item got minor changes, and several have been completely rewritten.

The FAQ's organization is rather different now, too. Many of the items from the previous "newbie" and "advanced" sections have been culled to make a new "intermediate" section. Another problem I fixed is that the old FAQ organization required that I always add new items at the end of a section instead of near related items. For the same reason, the previous FAQ organization didn't allow me to delete or move items. For these reasons and others, if you had hyperlinks to particular items on these pages, they are definitely now broken!

Most importantly for you, the reader, is that I've made quite an effort to make this FAQ more maintainable. Hopefully this will decrease the amount of procrastinating I do, so changes and additions will get done on a more timely schedule.

Previous "What's New" Entries...

What Is It That You Want, Exactly? :)

4/24/2000 - I just took a look at the keyword report that the FAQ's search engine puts out. This tells me what people are looking for most often in the FAQ. I fixed the number one item with a better section title. The second most-used term is "UDP", something this FAQ doesn't cover. So, I want to know what it is you are looking for, specifically. Send me an email telling me what you're having trouble with when using UDP.

Section 0 - Introduction

• The Original Introduction
  
• A Bit About the Maintainer
  
• Legal Stuff
  
• Mirrors
  
• What if your question is not in the FAQ?
  
• Language Bias
  
• Acknowledgements
  

Section 1 - General Winsock Information

• What is Winsock?
  
• What is the latest version?
  
• What does Winsock 2 have that Winsock 1.1 doesn't?
  
• When is the next rev of the specification due out?
  
• Can Winsock speak { DECNet, IPX/SPX, etc. }?
  
• Where can I get Winsock?
  
• Can I get Winsock 2 for...?
  
• Is there a version of Winsock for { OS/2, DOS, Unix, etc. }?
  

Section 2 - Issues for New Winsock Programmers

• Are there any sample apps on the Net?
  
• Do I need to initialize the WSAData structure before calling WSAStartup?
  
• I'm getting link errors when compiling Winsock programs. What's wrong?
  
• If I write a Winsock program, will I be able to communicate with a Unix Sockets program?
  
• Can I use Winsock with { My Favorite Language }?
  
• Are there any tools available for debugging Winsock programs?
  
• How do I get a readable error message from a Winsock error number?
  
• Winsock keeps returning the error WSAEWOULDBLOCK. What's wrong with my program?
  
• What can you tell me about MFC's CSocket and CAsyncSocket?
  
• How can I test my Winsock application without setting up a network?
  
• What's the proper way to close a TCP socket?
  
• Is it possible to close the connection "abnormally"?
  
• How do I detect when my TCP connection is closed?
  
• How do I detect an abnormal network disconnect?
  
• How can I change the timeout for a Winsock function?
  

Section 3 - Intermediate Winsock Issues

• How do I speak { HTTP, POP3, SMTP, FTP, Telnet, NNTP, etc. } with Winsock?
  
• How do I get my IP address from within a Winsock program?
  
• What's the proper way to impose a packet scheme on a stream protocol like TCP?
  
• How do I write my program to work through a firewall?
  
• I'm writing a server. What's a good network port to use?
  
• I'm having trouble porting a BSD sockets program to Winsock. Help!
  
• How do I send a broadcast packet?
  
• When should I turn off the Nagle algorithm?
  
• Is Winsock thread-safe?
  
• If two threads in an application call recv() on a socket, will they each get the same data?
  
• Is there any way for two threads to be notified when something happens on a socket?
  
• How do I detect if the modem is connected?
  
• How can I get the local username?
  
• Windows 9x's Dial Up Networking keeps popping up an automatic dial window, even when it isn't necessary. Can I make it stop?
  

Section 4 - Advanced Winsock Issues

• How can I open a raw data socket?
  
• How can I capture packets on a LAN with Winsock?
  
• How can I change the IP or TCP header of a packet?
  
• How can I "ping" another machine with Winsock?
  
• How do I pass a socket from one process to another?
  
• Is it possible to create sockets that map to a DLL rather than an application?
  
• How can I get access to the {route, ARP, interface, etc.} table?
  
• How do I get the MAC (a.k.a. hardware) address of the local Ethernet adapter?
  
• How many simultaneous sockets can I have open with Winsock?
  
• Can I change FD_SETSIZE to make select() wait on more than 64 sockets?
  
• How do I make Winsock use a specific network interface?
  
• What is the { SYN, ACK, FIN, RST } bit?
  
• Is it a bad idea to bind() to a particular port in a client program?
  

Section 5 - Resources

• Winsock Libraries and Controls
  
• Sample Winsock Applications and Tutorials
  
• Web Pages
  
• Winsock SDKs and Specifications
  
• Debugging Tools (packet sniffers and shims)
  
• Miscellaneous
  

Section 6 - Examples

• Several Basic Winsock Programs
  
• Pinging a Host Using Microsoft's ICMP.DLL
  
• Pinging a Host Using Raw Sockets
  
• How to Pass a Socket Handle in Win32
  
• Getting the Local IP Address
  
• Getting the Network Interface List
  
• How to Get the MAC (a.k.a. "hardware") Address, NetBIOS method
  
• How to Get the MAC (a.k.a. "hardware") Address, SNMP method
  
• How to Get the MAC (a.k.a. "hardware") Address, RPC method
  
• Finding the Maximum Number of Open Sockets
  
• How to Get the Local User Name
  

Section 7 - Articles

• Winsock for the Impatient by Warren Young
  
• Which I/O Strategy Should I Use? by Warren Young
  
• How to Use TCP Effectively by Warren Young
  
• The Lame List by the Winsock Vendor Community
  
• Debugging TCP by Warren Young
  
• Winsock's Compatibility With BSD Sockets by Warren Young
  
• WsControl() Revealed by Tom Sanfilippo
  

Section 8 - Reviews

Section 9 - Glossary

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