Windows API Reference

Protocol-Specific Information

This section details information relevant to specific network protocols supported by Winsock. Understanding these details is crucial for developing robust and efficient network applications.

TCP/IP Considerations

The Transmission Control Protocol (TCP) and Internet Protocol (IP) suite are the foundational protocols for most network communication on Windows. When working with TCP/IP sockets, consider the following:

• Connection-Oriented Communication: TCP provides reliable, ordered, and error-checked delivery of a stream of bytes. This means you need to establish a connection before sending data and handle connection establishment and teardown explicitly.
• Datagram Communication: IP, often used with UDP (User Datagram Protocol), provides a connectionless datagram service. Data is sent in independent packets (datagrams), and delivery is not guaranteed. Applications must handle potential packet loss and out-of-order delivery.
• Port Numbers: Both TCP and UDP use port numbers to distinguish between different services or applications running on the same host. Common ports (e.g., 80 for HTTP, 443 for HTTPS) are well-defined.

Key Winsock Functions for TCP/IP:

• socket(): To create a TCP or UDP socket.
• bind(): To associate a local address and port with a socket.
• connect(): To establish a connection to a remote host (TCP).
• listen() / accept(): For server applications to accept incoming connections (TCP).
• send() / recv(): For sending and receiving data.
• sendto() / recvfrom(): For sending and receiving datagrams (UDP).

Other Protocols

While TCP/IP is dominant, Winsock supports other protocols through different address families and protocol identifiers. These might include:

• NetBIOS: A legacy networking protocol.
• IPX/SPX: Novell's networking protocols, less common now.

When using these protocols, ensure that the corresponding protocol drivers are installed and configured correctly on the system. The address family and protocol type passed to the socket() function will dictate the protocol being used.

Protocol Information Structures

Winsock provides specific structures to carry protocol-dependent information. For example, when dealing with IP, you'll commonly use structures like sockaddr_in.

struct sockaddr_in {
    short            sin_family;   // AF_INET
    unsigned short   sin_port;     // Port number
    struct in_addr   sin_addr;     // IP address
    char             sin_zero[8];  // Not used
};
            

For IPv6, the sockaddr_in6 structure is used.