Socket网络编程
- 1. Socket网络编程
- 2. 大纲 • TCP/UDP • Socket • HTTP • Unix IO 模型
- 3. TCP-UDP 对比
- 4. UDP • User Datagram Protocol
- 5. TCP • Transmission Control Protocol
- 6. TCP——连接建立 • Before a client attempts to connect with a server, the server must first bind to and listen at a port to open it up for connections: this is called a passive open. Once the passive open is established, a client may initiate an active open. – SYN: The active open is performed by the client sending a SYN to the server. The client sets the segment's sequence number to a random value A. – SYN-ACK: In response, the server replies with a SYN-ACK. The acknowledgment number is set to one more than the received sequence number (A + 1), and the sequence number that the server chooses for the packet is another random number, B. – ACK: Finally, the client sends an ACK back to the server. The sequence number is set to the received acknowledgement value i.e. A + 1, and the acknowledgement number is set to one more than the received sequence number i.e. B + 1.
- 7. TCP——连接关闭 • The connection termination phase uses a four-way handshake, with each side of the connection terminating independently. • When an endpoint wishes to stop its half of the connection, it transmits a FIN packet, which the other end acknowledges with an ACK. • Therefore, a typical tear-down requires a pair of FIN and ACK segments from each TCP endpoint. • After both FIN/ACK exchanges are concluded, the side which sent the first FIN before receiving one waits for a timeout before finally closing the connection, during which time the local port is unavailable for new connections; this prevents confusion due to delayed packets being delivered during subsequent connections.
- 8. TCP——连接关闭
- 9. TCP——整个过程
- 10. TCP——netstat • LISTEN • (server) represents waiting for a connection request from any remote TCP and port. • SYN-SENT • (client) represents waiting for a matching connection request after having sent a connection request. • SYN-RECEIVED • (server) represents waiting for a confirming connection request acknowledgment after having both received and sent a connection request. • ESTABLISHED • (both server and client) represents an open connection, data received can be delivered to the user. The normal state for the data transfer phase of the connection.
- 11. TCP——netstat • FIN-WAIT-1 • (both server and client) represents waiting for a connection termination request from the remote TCP, or an acknowledgment of the connection termination request previously sent. • FIN-WAIT-2 • (both server and client) represents waiting for a connection termination request from the remote TCP. • CLOSE-WAIT • (both server and client) represents waiting for a connection termination request from the local user. • CLOSING • (both server and client) represents waiting for a connection termination request acknowledgment from the remote TCP. • LAST-ACK • (both server and client) represents waiting for an acknowledgment of the connection termination request previously sent to the remote TCP (which includes an acknowledgment of its connection termination request). • TIME-WAIT • (either server or client) represents waiting for enough time to pass to be sure the remote TCP received the acknowledgment of its connection termination request. • CLOSED • (both server and client) represents no connection state at all.
- 12. Socket • A network socket is an endpoint of an inter-process communication flow across a computer network. Today, most communication between computers is based on the Internet Protocol; therefore most network sockets are Internet sockets. • A socket API is an application programming interface (API), usually provided by the operating system, that allows application programs to control and use network sockets. Internet socket APIs are usually based on the Berkeley sockets standard. • A socket address is the combination of an IP address and a port number, much like one end of a telephone connection is the combination of a phone number and a particular extension. Based on this address, internet sockets deliver incoming data packets to the appropriate application process or thread.
- 15. Socket——选项 • SO_DEBUG • SO_DONTROUTE • SO_KEEPALIVE • SO_DONTLINER • SO_LINGER • SO_RCVBUF • SO_SNDBUF • SO_REUSERADDR • SO_RCVTIMEO • SO_SNDTIMEO • TCP_NODELAY(Nagle)
- 16. HTTP • Hypertext Transfer Protocol • HTTP functions as a request-response protocol in the client-server computing model.
- 17. HTTP——Request • Request methods – HEAD/GET/POST/PUT/DELETE/TRACE/OPTIONS/C ONNECT/PATCH
- 18. HTTP——GET POST • GET 参数 • POST 参数 – application/x-www-form-urlencoded – multipart/form-data(non-ASCII data, and binary data)
- 23. HTTP——Response • Status codes – 1xx Informational/2xx Success/3xx Redirection/4xx Client Error/5xx Server Error
- 28. HTTP——Persistent connections • Persistent connections – In HTTP/0.9 and 1.0, the connection is closed after a single request/response pair. In HTTP/1.1 a keep-alive-mechanism was introduced, where a connection could be reused for more than one request.
- 29. Unix IO 模型 • Unix下共有五种I/O模型 – 阻塞I/O – 非阻塞I/O – I/O复用（select和poll） – 信号驱动I/O（SIGIO） – 异步I/O（Posix.1的aio_系列函数）
- 30. Unix IO 模型——阻塞IO
- 32. Unix IO 模型——IO复用
- 34. Unix IO 模型——异步IO
- 35. Unix IO 模型——对比
- 36. Unix IO 模型——异步IO
- 37. END