linux socket的select函数例子

Love The Way You Lie 2021-11-16 12:32 318阅读 0赞

转自:[http://www.cnblogs.com/faraway/archive/2009/03/06/1404449.html][http_www.cnblogs.com_faraway_archive_2009_03_06_1404449.html]

使用select函数可以以非阻塞的方式和多个socket通信。程序只是演示select函数的使用，功能非常简单，即使某个连接关闭以后也不会修改当前连接数，连接数达到最大值后会终止程序。

1. 程序使用了一个数组fd\_A，通信开始后把需要通信的多个socket描述符都放入此数组。

2. 首先生成一个叫sock\_fd的socket描述符，用于监听端口。

3. 将sock\_fd和数组fd\_A中不为0的描述符放入select将检查的集合fdsr。

4. 处理fdsr中可以接收数据的连接。如果是sock\_fd，表明有新连接加入，将新加入连接的socket描述符放置到fd\_A。

\#include  < stdio.h >   
\#include  < stdlib.h >   
\#include  < unistd.h >   
\#include  < errno.h >   
\#include  < string .h >   
\#include  < sys / types.h >   
\#include  < sys / socket.h >   
\#include  < netinet / in .h >   
\#include  < arpa / inet.h >   
  
 \#define  MYPORT 1234  //  the port users will be connecting to   
  
 \#define  BACKLOG 5  //  how many pending connections queue will hold   
  
 \#define  BUF\_SIZE 200   
  
 int  fd\_A\[BACKLOG\];  //  accepted connection fd   
 int  conn\_amount;  //  current connection amount   
   
 void  showclient()  
\{  
 int  i;  
printf( " client amount: %d\\n " , conn\_amount);  
 for  (i  =  0 ; i  <  BACKLOG; i \++ ) \{  
printf( " \[%d\]:%d  " , i, fd\_A\[i\]);  
\}  
printf( " \\n\\n " );  
\}  
  
 int  main( void )  
\{  
 int  sock\_fd, new\_fd;  //  listen on sock\_fd, new connection on new\_fd   
  struct  sockaddr\_in server\_addr;  //  server address information   
  struct  sockaddr\_in client\_addr;  //  connector's address information   
  socklen\_t sin\_size;  
 int  yes  =  1 ;  
 char  buf\[BUF\_SIZE\];  
 int  ret;  
 int  i;  
  
 if  ((sock\_fd  =  socket(AF\_INET, SOCK\_STREAM,  0 ))  ==  \- 1 ) \{  
perror( " socket " );  
exit( 1 );  
\}  
  
 if  (setsockopt(sock\_fd, SOL\_SOCKET, SO\_REUSEADDR,  & yes,  sizeof ( int ))  ==  \- 1 ) \{  
perror( " setsockopt " );  
exit( 1 );  
\}  
  
server\_addr.sin\_family  =  AF\_INET;  //  host byte order   
  server\_addr.sin\_port  =  htons(MYPORT);  //  short, network byte order   
  server\_addr.sin\_addr.s\_addr  =  INADDR\_ANY;  //  automatically fill with my IP   
  memset(server\_addr.sin\_zero,  ' \\0 ' ,  sizeof (server\_addr.sin\_zero));  
  
 if  (bind(sock\_fd, ( struct  sockaddr  \* ) & server\_addr,  sizeof (server\_addr))  ==  \- 1 ) \{  
perror( " bind " );  
exit( 1 );  
\}  
  
 if  (listen(sock\_fd, BACKLOG)  ==  \- 1 ) \{  
perror( " listen " );  
exit( 1 );  
\}  
  
printf( " listen port %d\\n " , MYPORT);  
  
fd\_set fdsr;  
 int  maxsock;  
 struct  timeval tv;  
  
conn\_amount  =  0 ;  
sin\_size  =  sizeof (client\_addr);  
maxsock  =  sock\_fd;  
 while  ( 1 ) \{  
 //  initialize file descriptor set   
  FD\_ZERO( & fdsr);  
FD\_SET(sock\_fd,  & fdsr);  
  
 //  timeout setting   
  tv.tv\_sec  =  30 ;  
tv.tv\_usec  =  0 ;  
  
 //  add active connection to fd set   
  for  (i  =  0 ; i  <  BACKLOG; i \++ ) \{  
 if  (fd\_A\[i\]  !=  0 ) \{  
FD\_SET(fd\_A\[i\],  & fdsr);  
\}  
\}  
  
ret  =  select(maxsock  \+  1 ,  & fdsr, NULL, NULL,  & tv);  
 if  (ret  <  0 ) \{  
perror( " select " );  
 break ;  
\}  else  if  (ret  ==  0 ) \{  
printf( " timeout\\n " );  
 continue ;  
\}  
  
 //  check every fd in the set   
  for  (i  =  0 ; i  <  conn\_amount; i \++ ) \{  
 if  (FD\_ISSET(fd\_A\[i\],  & fdsr)) \{  
ret  =  recv(fd\_A\[i\], buf,  sizeof (buf),  0 );  
 if  (ret  <=  0 ) \{  //  client close   
  printf( " client\[%d\] close\\n " , i);  
close(fd\_A\[i\]);  
FD\_CLR(fd\_A\[i\],  & fdsr);  
fd\_A\[i\]  =  0 ;  
\}  else  \{  //  receive data   
  if  (ret  <  BUF\_SIZE)  
memset( & buf\[ret\],  ' \\0 ' ,  1 );  
printf( " client\[%d\] send:%s\\n " , i, buf);  
\}  
\}  
\}  
  
 //  check whether a new connection comes   
  if  (FD\_ISSET(sock\_fd,  & fdsr)) \{  
new\_fd  =  accept(sock\_fd, ( struct  sockaddr  \* ) & client\_addr,  & sin\_size);  
 if  (new\_fd  <=  0 ) \{  
perror( " accept " );  
 continue ;  
\}  
  
 //  add to fd queue   
  if  (conn\_amount  <  BACKLOG) \{  
fd\_A\[conn\_amount \++ \]  =  new\_fd;  
printf( " new connection client\[%d\] %s:%d\\n " , conn\_amount,  
inet\_ntoa(client\_addr.sin\_addr), ntohs(client\_addr.sin\_port));  
 if  (new\_fd  >  maxsock)  
maxsock  =  new\_fd;  
\}  
 else  \{  
printf( " max connections arrive, exit\\n " );  
send(new\_fd,  " bye " ,  4 ,  0 );  
close(new\_fd);  
 break ;  
\}  
\}  
showclient();  
\}  
  
 //  close other connections   
  for  (i  =  0 ; i  <  BACKLOG; i \++ ) \{  
 if  (fd\_A\[i\]  !=  0 ) \{  
close(fd\_A\[i\]);  
\}  
\}  
  
exit( 0 );  
\}

转载于:https://www.cnblogs.com/hnrainll/archive/2011/05/05/2038241.html

[http_www.cnblogs.com_faraway_archive_2009_03_06_1404449.html]: http://www.cnblogs.com/faraway/archive/2009/03/06/1404449.html