TCP/IP Programming in Windows

This section provides comprehensive guidance and API references for developing network applications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite on Windows.

Introduction to TCP/IP

TCP/IP is the foundational protocol suite for the internet and most modern networks. It provides a reliable, connection-oriented communication service, making it suitable for a wide range of applications, from web browsing to file transfers.

Key Concepts

• Sockets: The primary interface for network communication. Windows Sockets (Winsock) provides a standardized API for accessing the TCP/IP protocol stack.
• IP Addresses: Unique identifiers for devices on a network (e.g., IPv4: 192.168.1.1, IPv6: 2001:0db8:85a3:0000:0000:8a2e:0370:7334).
• Ports: Numbers used to identify specific applications or services running on a device.
• Connection Establishment: The three-way handshake (SYN, SYN-ACK, ACK) used to set up a TCP connection.
• Data Transmission: Reliable, ordered delivery of data streams.
• Error Handling: Mechanisms for detecting and recovering from network errors.

Core Winsock APIs

The Winsock API is your gateway to TCP/IP programming on Windows. Here are some of the most fundamental functions:

SOCKET socket(
  [in] int af,
  [in] int type,
  [in] int protocol
);

int bind(
  [in] SOCKET s,
  [in] const struct sockaddr *name,
  [in] int namelen
);

int connect(
  [in] SOCKET s,
  [in] const struct sockaddr *name,
  [in] int namelen
);

int send(
  [in] SOCKET s,
  [in] const char *buf,
  [in] int len,
  [in] int flags
);

int recv(
  [in] SOCKET s,
  [in] char *buf,
  [in] int len,
  [in] int flags
);

int listen(
  [in] SOCKET s,
  [in] int backlog
);

SOCKET accept(
  [in] SOCKET s,
  [out] struct sockaddr *addr,
  [in, out] int *addrlen
);

Building a TCP Client/Server Application

Follow these general steps to create a basic TCP client and server:

1. Client: Create a socket, resolve the server address, connect to the server, send/receive data, and close the socket.
2. Server: Create a socket, bind it to a local address and port, listen for incoming connections, accept a connection, send/receive data, and close the client socket. Repeat accept for multiple clients.

Example: Simple Echo Server

Refer to the Echo Server Sample for a practical implementation.

Advanced Topics

• Asynchronous I/O (Overlapped I/O)
• Socket Options
• Network Event Notification (WSAEventSelect, WSAAsyncSelect)
• IPv6 Support
• Security Considerations