What is the purpose of the network? For information transmission, acceptance can link the information of various points, polygons and bodies to the shared OSI model: Application layer: Provider service presentation layer: Data encryption, optimization, compression Session Layer: Establish link, transport service Transport layer: Provide data transfer service Network layer: Routing network interconnection Overlay: Link Exchange physical layer: Hard components, interfaces, network card requirements features: functions are separated to achieve high cohesion low coupling make development clearer What is a network protocol? is a set of rules, conventions, standards protocols used by each model: application layer: TFTP (file transfer), HTTP (Hypertext Transfer Protocol), DNS ( Domain name resolution), SMTP (mail transport) Transport layer: TCP (for reliable transport services with links), UDP (non-connected transport dependent service) Network layer: IP (IP address) Common IPV4: Dotted decimal Value 0~256 (32-bit) ipv6::128 bit Physical layer:ieee special ip: 127.0.0.1 native ip 0.0.0.0 automatically use locally available network cards ip 192.168.1.0 represent network segments 192.168.1.1 typically gateway address 192.198.1.255 broadcast address port: value range 1~65535 1~255 Some general-purpose ports 256~1023 SystemsPorts 1024~65535 own ports linux command: ifconfig View native ip ping ip View Latency ps-aux View system process information chmod Set file permissions &NB Sp nice-9 ./hello.py run with 9 priority pstree View process tree ps-ajx& nbsp View Parent-child process idlinux under File type: bcd-lsp b (fast device file) &nbs P c (character device files) &NBSP;D (catalogue) -(normal file) &NBSP ; l (link file) s (socket file) p (pipeline file) ps-aux& nbsp Stat of Query result indicates process status: d wait state block non-interruptible wait state s wait state sleep interruptible wait State &nb Sp t Wait state pause Pause execution r run (ready state) z zombie + ago Process (running at terminal) &NBSp < higher priority processes n lower-priority processes s reply-to-group l child process link process priority: value range:-20~19 -20 Max Python Socket Module socket.gethostname () Get native name socket.gethostbyname ("hostname") Get ip soccket.gethostbtname ("IP") from the hostname get the 16 binary conversion: of the local ipip Socket.inet_aton (IP) decimal to hex SOCKET.INET_ATOA (hex) hexadecimal to decimal Socket.gethostbyaddr (' 127.0.0.1 ') return value: Tuple (host, alias, IP address) Socket.getservbyname ("program name") Get program ports Sockets: Sockets programming excuses provided by programming language Transport Layer Services: TCP: (SOCK_STREAM) Reliable transport services for linked streaming sockets 1. Creating sockets: socket = Socke T.socket () 2. Binding address: &NBSP; socket.bind 3. Set monitoring: socket.listen () 4. Waiting for client links: socket.accept () 5. Messaging: SOCKET.RECV (4096) socket.send ("") &NBSP ; 6. Close socket: Socket.close () client: &NBSP ; 1. Creating sockets Socket.socket.socket () &NBSP;2. Initiating links & nbsp socket.connect (address) 3. Messaging &N Bsp &NBSP;SOCKET.RECV (1024x768) Close news socket . Send ("") send messages socket.sendall (): &NB Sp Things send messages successfully return none failed exception 4. Close socket & nbsp Socket.close () recv features: Building the other end of the link is broken and returns a Empty string fetch content from buffer Send attribute: Other end impure in producing a pipe broken exception to buffer Write content buffers: reduce and interact with disk to coordinate data delivery efficiency Sticky pack: &nbs P Because TCP is a data flow socket each time the data is sent between No boundary one time to fetch the next data will form a sticky package & nbsp; UDP: (sock_dgram) non-connected unreliable transport service datagram sockets 1. Creating Sockets: & nbsp socket = Socket.socket (af_inet,sock_dgram) 2. Binding address: &NB Sp Socket.bind () 3. Send and receive messages: Socket.recvfrom () & nbsp &nbsP Socket.sento () 4. Close socket: socket.close () &N Bsp Client: 1. Create socket: socket = Socket.socket () &n Bsp 2. Send and receive messages; Socket.recvform () Socket.sendto ("", address) 3. Close socket: SO Cket.close () sys.argv () command line get parameter return value: tuple: sys.argv[0] Start space delimited quotation marks Socket property method: Socket Properties: socket.type Address type: &NB Sp socket.family Socket IO descriptor: Socket.fileno () & nbsp System IO descriptor: sys.stdin = 0 &nbs P   sys.stdout = 1 sys.stderr = 2   ; Get socket address: socket.getsockname () GET socket client Address: socket.getpeername () set up port reuse: &NBSP ; socket.setsockopt (Sol_socket, SO_REUSEADDR, 1) GET socket option values: & nbsp socket.getsockopt () set to non-blocking status: Socket.setblocking (False) Timeout detection: Socket.settimeout (SEC) http Protocol (Hypertext Transfer Protocol): Web browser a protocol to get a webpage and all www. Files must comply with this standard http request: 1. Request Line: Description of specific request categories and content GET /INDEX.HTML&NBsp /http/1.1 request category request content protocol version   ; Request category: GET: Get network resources &NB Sp POST: Submit certain additional data HEAD: & nbsp Get response header PUT: Update server resource &NB Sp DELETE: Delete server resources CONNECT: &nbs p; not used TRACE: for testing optio ns: Get server performance information 2. Request Header: Request specific description &NBSP ; 3. Blank line 4. Request Body: specific parameters or submitted content HTTP response: 1. Response Line: Feedback specific The ringDue http/1.1 20 OK &NBS P Version Agreement Response Code additional information response: &NBSP;1XX: Indicates that the request has been received &NBSP;2XX: Response success 3XX: Response needs to be directed (re-record link to third party link) &NBSP;4XX: Client error 5XX: Server-side error 2. Response header: Detailed description of response content 3. Blank line &N Bsp 4. Response Body: return client request content IO: The operation of data exchange in memory can be considered as IO operation (input/output) IO Intensive program: Lots of IO operations, consumes less CPU CPU-intensive programs: A lot of memory CPU operation, IO relatively less IO classification: blocking io: Because some conditions are not achieved cause the program to jam such as: input function non-blocking IO: Change the state of the blocking function to block IO multiplexing: &NBSPThrough a monitoring monitoring of the behavior of multiple IO events, which IO event is ready to execute which IO event io is ready: Critical state when IO event is about to occur select module Monitoring IO events RS, WS, XS = select (Rlist, Wlist, xlist[, timeout]) rlist: pending io wlist: actively processing io X list: error io bit operation to be processed: bitwise operation according to Bits & press as with | bitwise OR ^ << left XOR >> Right-shift poll method for IO multiplexing: 1. Creating poll Objects: p = select.poll 2. Register the following io: p.register (s, Pollin | Pllerr) not interested: P.unregister (s) event Category: & nbsp pollin pollout pollerr pollhup POLLPRI &NBS P rlist &NBSP;WList xlist break Emergency handling   ; 3. Monitoring io: events = P.poll () Features: monitoring the IO events of interest &NBS p; return value: Return an IO event occurred events is a list [(Fileno, Evnet), (), () ....] Each Ready IO corresponds to a tuple (descriptor, ready event) io map: {S.fileno ():s} 4. Handling IO Events & nbsp; local sockets: functions: data transfer between different programs for local files Local socket transfer process: 1. Create a local socket object SOCKFD = socket (Af_unix, sock_stream) 2. Bind a socket file, as If the file does not exist then it will be created automatically if there is an error sockfd.bind (file) 3. Monitoring nbsp;listen 4. Messaging &NBSP;RECV send multitasking programming: The use of multiple cores of the computer to achieve simultaneous execution of multiple tasks thus achieveThe purpose of the operation efficiency of the program parallel: Multiple computer cores are simultaneously working on multiple tasks, Then multiple tasks are parallel relationships and nbsp Concurrent: running multiple tasks simultaneously, the kernel is constantly switching between multiple tasks, Achieving the processing effect that multiple tasks will perform & nbsp There are concurrent relationships between tasks Programs: executables, which are static and only occupy disk process: & nbsp is a dynamic process program running &NBSP;CPU time slice: If there is a process that occupies the CPU at this point, we call the process a CPU time slice multiple process tasks or rotating CPU time slices to form the concurrency effect process features: process is the smallest unit of operating system allocated resources Each process has its own independent running space (4 g of virtual memory space) & nbsp The processes are independent of each other and do not affect the status of process: Tri-State: ready State: &NBSP ; process with execution conditions, waiting for system to allocate processor resources into run state run: &NB Sp process occupied CPU is running Wait state: process temporarily does not have operating conditions, need to block wait Five-state: &NBSP ; Add new and terminated states on a tri-state basis new: &N Bsp Create a new program, get system resources process End: &NBS P Process execution end, freeing the resource process os module: Determining if a file exists: os.path.exists (file) Delete files: os.remove (file) os.unlink (file) Create process: os.fork () get process id: os.getpid () Get parent process id: os.getppid () quit a process: os.exit () & nbsp sys.exit (exit hint) sYs.exit () can exit orphan process by capturing Systemexit exception: When the parent process exits the child process, the child process becomes an orphan process The orphan process is automatically processed by the system when the process is adopted exited the zombie process: When the child process takes precedence over the parent process exits, the parent process does not process the child process's exit status It becomes a zombie process Zombie process stuck PCB consumes memory resources How to avoid zombie process generation: 1. Parent process exits 2. Parent process processes subprocess status process zombie process: & nbsp pid,status = os.wait (): wait blocking the exit of the waiting process subprocess in the parent process &N Bsp fear PID and exit status of returned subprocess pid,status = Os.waitpid (pid,option): waitpid in parent process block wait for processing subprocess exit parameters: &NBSP ; pid -1 means waiting for any sub-process to exit &NB Sp >0 indicates that the subprocess waiting for the corresponding PID number exits option 0 Blocking wait Wnohang represents non-blocking Return of retired subprocess PID and exit status using level two subprocess: Parent process Create child process wait process exit Child process create next process and exit immediately Level two sub-process becomes orphan process handling specific work multiprocessing module process () Features: Create process object parameters: target: Function object &NB Sp;name to the process new name () args: Tuple used to give the target function location parameters kwargs: The dictionary is used to pass the target function key value nbsp START process: p.start () Call binding function There are child processes running waiting for the child process to exit: p.join ([timeout detection]) do not use join to reclaim possible zombie processes after Using multiprocessing to create a process child process also replicates all the memory space of the parent process has its own independent space to execute the non-interfering sub-process also has its own PID specific resources Using multiprocessing to create child processes, the general parent process feature is used only to create child processes Reclaim child processes, return events to the child process to complete
Python network programming (weekly Summary1)
