poll code

Unfortunately, this morning I encountered a select problem. Fortunately, I/O processing modules of the Network were encapsulated. This afternoon, I/O processing encapsulation Based on Poll was completed quickly, You only need to replace one line of code to easily switch from the select architecture to poll, and also to epoll. You can switch the network I/O proces

To thoroughly understand poll or understand the following code, please refer to the "Linux network programming--i/o multiplexing poll function"Code:#include Operation Result:Source Download:Linux Network Programming--tcp Concurrent Server (poll implementation)

On this topic, the online has been introduced more, here is just a flowchart to make a simple and clear comparison, convenient to distinguish.First, select/poll realization mechanismCharacteristics:1.select/poll each time it needs to pass all the listening fd in, involving the user space and the direct data copy of the kernel.2.FD Event callback function is Pollwake, just wake up the process, this will need

, the kernel to dispatch other process to run, passive loses CPU. (Hangs can be preempted by another process, causing it to hang, or to suspend itself on its own initiative.) ) 5 I/O models available under UNIX: 1, blocking I/O 2, non-blocking I/O 3,i/o multiplexing 4, signal-driven I/O (SIGIO) 5, asynchronous i/o1--4 for synchronous i/o,5 for asynchronous I/O. The I/O multiplexing we are concerned with is synchronous I/O, which causes the process to block.There are horizontal triggers in the IO

1. SelectSelect essentially processes the next step by setting or checking the data structure that holds the FD flag bit.Disadvantages:1) The number of FD that can be monitored by a single process is limited.2) The need to maintain a data structure to hold a large number of FD, which will make the user space and kernel space in the transfer of the structure when the replication overhead.3) A linear scan is performed when the FD is scanned. After the FD surge, the IO efficiency is low because eac

A blocking/nonblocking method is available when an application accesses a device file. If you are using blocking mode, call Open (), read (), write () directly, but the driver layer will determine whether it is readable/writable, and if unreadable/not writable, the current process will hibernate until it wakes up. If you are using non-blocking, you need to use the poll/select mechanism, and the access to the tag file is o_nonblock when you open the fi

The poll system call is similar to select and polls a certain number of file descriptors within a specified time to test if there is a ready person. Poll and select efficiency is similar, but its use of the interface is relatively simple, poll is not limited to 1024 file descriptors, poll listener events and trigger ev

collection of abnormal descriptive words of interest, that is, when a descriptive word in the collection encounters an exception, it will receive a notification from the kernel. Timeout Used to specify the timeout length. This is a struct. Struct timeval {long TV _sec; // number of seconds long TV _usec; // Number of microseconds} Usage Details UNP Third Edition Difference between epoll and select/poll: 1. support a proces

For objective reasons, the new developments in Linux have failed to keep up with the new development of the Linux kernel, especially in the ever-changing Linux kernel. This article explains the main differences between select/poll in UNIX and epoll in Linux. 1. support a process to open a large number of socket Descriptors (FD) The most intolerable thing about select isThe FD opened by a process has certain limitations.,Fd_setsizeSet, the default

About I/O multiplexing:I/O multiplexing (also known as "event-driven") is the first thing to understand. The operating system provides you with a feature. When one of your sockets is readable or writable. It can give you a notice. When used with a non-clogging socket, it is only when the system notifies me which descriptive descriptor is readable that I run the read operation. The ability to ensure that every read reads valid data without making a pure return-1 and Eagain. Write operations are s

All three are UNIX-based multiplexing kernel interfaces. Select is a cross-platform interface, poll is the systemv standard, and epoll is a proprietary Linux interface, which is transformed Based on Poll. Select Function prototype: Int select (int n,Fd_set * readfds,Fd_set * writefds,Fd_set * required TFDs,Struct timeval * timeout );The SELECT statement monitors arrays of multiple file descriptors through s

We're up to the top. With file operations combined with select and poll, blocking operations can be implemented.Select interface:int select (int Nfds, fd_set *readset, Fd_set *writeset,Fd_set *exceptset, struct timeval *timeout);whichNfdsThe number of file descriptors that need to be checked, the value should be the maximum number in the three groups of Fd_setLarger, rather than the total number of actual file descriptors.ReadsetA set of file descript

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or more keywords to accomplish a given task. Statements can be simple, such as notification functions exiting, or complex, such as specifying the number of times a command can be repeatedly executed. The following table lists the syntax and purpose of most JavaScript statements:About Nvelocity no longer introduce too much, such an article has too many, I just wrap it up for use, the problems encountered in it will be explained in one. Why use the template engine is because to define a different

not be said to be redundant see the detail sectionThis is interesting, Django tutorial intimate judgment is not a plural, anyway, if not ask, I also forget what the label is doing, so that the view is not particularly glaring?Let's take a look at the final effectOkay, now the official Django example is done,The rest of it is about CBV, but Web2py doesn't supportSo this tutorial is an introduction,Just to tell you that the sameBut each framework has its own desirable things, such as if there is

You can use the following code to read data from a socket: While (n = read (socketfd, Buf, bufsize)> 0) If (write (stdout_fileno, Buf, n) = N) { Printf ("write error "); Exit (1 ); } When the file table item corresponding to the socketfd descriptor in the Code is blocked, it will be blocked until data is sent from the other end of the network. If it is a server program that needs to read and write a large n

IO multiplexing: A process can monitor multiple descriptors and, once a descriptor is read-ready or written, notifies the process program to read and write accordinglyUsage scenarios:1. When the customer processes multiple descriptors (network sockets) or one customer processes multiple sockets simultaneouslyThe 2.TCP server handles both the listener socket interface and the connected socket.3. One server to handle multiple services or multiple protocols also use I/O multiplexingThe maximum bene

When using socket or serial port, application code often uses select to determine whether data is received or not. What processing does the driver need? Can the application-layer users correctly determine whether data is received and read? Using select can monitor the changes in the file descriptor we need to monitor-read/write or exception.First, a simple model is created. The application uses select to monitor whether the device is readable. When th

Trigger project; Poll SCM: Periodically check the source changes (according to the version number of the SCM software), if there is an update checkout the latest code down, and then perform the build action. The following figure configuration:/5 * * * (check the source change every 5 minutes) Build periodically: The cycle of project construction (it does not care whether the source is changed), as shown i

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