select 函数使用方法（Select function usage）.docVIP

select 函数使用方法（Select function usage） Using the select function method 2011-08-15 16:36 663 (0) of the report read comments Select in Socket programming is very important, but for beginners Socket people do not love to write programs in Select, they are just used to write accept, such as connect, recv or recvfrom like block (block, the so-called blocking mode as the name suggests, is the process or thread to perform these functions must be waiting to happen, an event if the event does not occur, processes or threads are blocked, the function can not be immediately returned). But you can use Select to complete the non blocking (non-block, the so-called non blocking way is the process or thread to perform this function does not have to happen, waiting for an event once the executive must return, to return a different value to reflect the implementation of the function, if the event is blocked and the same way, if the incident did not happen to return a code to inform the event does not occur, and the process or thread to continue, so high efficiency) of work procedures, it can monitor the changes we need to monitor the file descriptor -- or abnormal. The following detailed introduction! The function of Select format (that is the Unix system under the socket programming under Windows Berkeley, and there is the difference between a description): Int select (int maxfdp, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout); The first description of the two structures: First, struct fd_set can be understood as a set, stored in the set file descriptor (filedescriptor), namely the file handle, which can be of general significance we call the Unix file, of course any equipment, pipelines, etc. are FIFO documents, all included, so there is no doubt a socket is a socket file, a handle is a file descriptor. The fd_set collection through macros to operate by human, such as the empty set FD_ZERO (fd_set *); A given file descriptor into the set FD_SET (int,