socket编程实践（Socket programming practice）.docVIP

socket编程实践（Socket programming practice） The 1.connect function returns to the call of the function after the interrupt returns. Practice has proved that for a non blocking socket, if when calling the connect function, if the interruption, this function responds to the interrupt, but when the interrupt return, continue to call the function connect, until the connect timeout failed or received ICMP packets or connection error 2.accept () If the listening process is working in a non blocking mode, when the accept () function receives the request from the client, the returned socket socket defaults to the blocked mode of operation. Block model There are four kinds of socket calls that may be blocked: 1. input operations: read, readv, recv, recvfrom, and recvmsg functions 2. output operations: write, writev, send, SendTo, and sendmsg functions 3. receive external connections: accept () function 4. initializes outgoing connections: connect () function Two, I/O model 1. block I/O 2. non blocking I/O 3.I/O multiplexing (select function) 4. signal driver I/O (SIGIO) 5. asynchronous I/O Three, I/O reuse model applications 1. when a client processes multiple descriptors (typically interactive inputs and network socket interfaces), I/O reuse must be used. 2., a client handles multiple sets of interfaces simultaneously 3., I/O reuse is also common if a TCP server is handling the listening socket interface and processing the connected socket interface. 4., if a server has to process TCP and process UDP, I/O reuse is also common. 5., if a server handles multiple services or multiple protocols (the inetd daemon). Four, denial of service attacks The server a time blocked in dealing with only a single customer, it can not deal with other customers, which led to a denial of service attack, possible solutions are: (a) the use of non blocking I/O model; (b) for each customer service provided by separate threads of control (for example, create a child process or for each thread to provid