socket编程的同步、异步与阻塞、非阻塞示例详解之二

接上文:
http://blog.chinaunix.net/uid-26000296-id-3755264.html
三、异步阻塞模式

另外一个阻塞解决方案是带有阻塞通知的非阻塞 I/O。

在这种模型中，配置的是非阻塞 I/O，然后使用阻塞 select 系统调用来确定一个 I/O 描述符何时有操作。

使 select 调用非常有趣的是它可以用来为多个描述符提供通知，而不仅仅为一个描述符提供通知。

对于每个提示符来说，我们可以请求这个描述符可以写数据、有读数据可用以及是否发生错误的通知

下面的C语言实现的例子，它从网络上接受数据写入一个文件中:

/*

* \brief

* tcp client

*/

#include <stdio.h>

#include <stdlib.h>

#include <sys/socket.h>

#include <sys/select.h>

#include <sys/time.h>

#include <netdb.h>

#include <string.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#define SERVPORT 8080

#define MAXDATASIZE 100

#define TFILE "data_from_socket.txt"

int main(int argc, char *argv[])

{

int sockfd, recvbytes;

char rcv_buf[MAXDATASIZE]; /*./client 127.0.0.1 hello */

char snd_buf[MAXDATASIZE];

struct hostent *host; /* struct hostent

* {

* char *h_name; // general hostname

* char **h_aliases; // hostname's alias

* int h_addrtype; // AF_INET

* int h_length;

* char **h_addr_list;

* };

*/

struct sockaddr_in server_addr;

/* */

fd_set readset, writeset;

int check_timeval = 1;

struct timeval timeout={check_timeval,0}; //阻塞式select, 等待1秒，1秒轮询

int maxfd;

int fp;

int cir_count = 0;

int ret;

if (argc < 3)

{

printf("Usage:%s [ip address] [any string]\n", argv[0]);

return 1;

}

*snd_buf = '\0';

strcat(snd_buf, argv[2]);

if ((fp = open(TFILE,O_WRONLY)) < 0) //不是用fopen

{

perror("fopen:");

exit(1);

}

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

{

perror("socket:");

exit(1);

}

server_addr.sin_family = AF_INET;

server_addr.sin_port = htons(SERVPORT);

inet_pton(AF_INET, argv[1], &server_addr.sin_addr);

memset(&(server_addr.sin_zero), 0, 8);

/* create the connection by socket

* means that connect "sockfd" to "server_addr"

*/

if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)

{

perror("connect");

exit(1);

}

/**/

if (send(sockfd, snd_buf, sizeof(snd_buf), 0) == -1)

{

perror("send:");

exit(1);

}

printf("send:%s\n", snd_buf);

while (1)

{

FD_ZERO(&readset); //每次循环都要清空集合，否则不能检测描述符变化

FD_SET(sockfd, &readset); //添加描述符

FD_ZERO(&writeset);

FD_SET(fp, &writeset);

maxfd = sockfd > fp ? (sockfd+1) : (fp+1); //描述符最大值加1

ret = select(maxfd, &readset, NULL, NULL, NULL); // 阻塞模式

switch( ret)

{

case -1:

exit(-1);

break;

case 0:

break;

default:

if (FD_ISSET(sockfd, &readset)) //测试sock是否可读，即是否网络上有数据

{

recvbytes = recv(sockfd, rcv_buf, MAXDATASIZE, MSG_DONTWAIT);

rcv_buf[recvbytes] = '\0';

printf("recv:%s\n", rcv_buf);

if (FD_ISSET(fp, &writeset))

{

write(fp, rcv_buf, strlen(rcv_buf)); // 不是用fwrite

}

goto end;

}

}

cir_count++;

printf("CNT : %d \n",cir_count);

}

end:

close(fp);

close(sockfd);

return 0;

}

perl实现:

#! /usr/bin/perl

###############################################################################

# \File

# tcp_client.pl

# \Descript

# send message to server

###############################################################################

use IO::Socket;

use IO::Select;

#hash to install IP Port

%srv_info =(

#"srv_ip" => "61.184.93.197",

"srv_ip" => "192.168.1.73",

"srv_port"=> "8080",

);

my $srv_addr = $srv_info{"srv_ip"};

my $srv_port = $srv_info{"srv_port"};

my $sock = IO::Socket::INET->new(

PeerAddr => "$srv_addr",

PeerPort => "$srv_port",

Type => SOCK_STREAM,

Blocking => 1,

# Timeout => 5,

Proto => "tcp")

or die "Can not create socket connect. $@";

$sock->send("Hello server!\n", 0) or warn "send failed: $!, $@";

$sock->autoflush(1);

my $sel = IO::Select->new($sock);

while(my @ready = $sel->can_read)

{

foreach my $fh(@ready)

{

if($fh == $sock)

{

while()

{

print $_;

}

$sel->remove($fh);

close $fh;

}

}

}

$sock->close();

四、异步非阻塞模式

最后，异步非阻塞 I/O 模型是一种处理与 I/O 重叠(并行)进行的模型。

以read系统调用为例

steps：

a. 调用read;

b. read请求会立即返回，说明请求已经成功发起了。

c. 在后台完成读操作这段时间内，应用程序可以执行其他处理操作。

d. 当 read 的响应到达时，就会产生一个信号或执行一个基于线程的回调函数来完成这次 I/O 处理过程。

/*

* \brief

* tcp client

*/

#include <stdio.h>

#include <stdlib.h>

#include <sys/socket.h>

#include <sys/select.h>

#include <sys/time.h>

#include <netdb.h>

#include <string.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#define SERVPORT 8080

#define MAXDATASIZE 100

#define TFILE "data_from_socket.txt"

int main(int argc, char *argv[])

{

int sockfd, recvbytes;

char rcv_buf[MAXDATASIZE]; /*./client 127.0.0.1 hello */

char snd_buf[MAXDATASIZE];

struct hostent *host; /* struct hostent

* {

* char *h_name; // general hostname

* char **h_aliases; // hostname's alias

* int h_addrtype; // AF_INET

* int h_length;

* char **h_addr_list;

* };

*/

struct sockaddr_in server_addr;

/* */

fd_set readset, writeset;

int check_timeval = 1;

struct timeval timeout={check_timeval,0}; //阻塞式select, 等待1秒，1秒轮询

int maxfd;

int fp;

int cir_count = 0;

int ret;

if (argc < 3)

{

printf("Usage:%s [ip address] [any string]\n", argv[0]);

return 1;

}

*snd_buf = '\0';

strcat(snd_buf, argv[2]);

if ((fp = open(TFILE,O_WRONLY)) < 0) //不是用fopen

{

perror("fopen:");

exit(1);

}

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

{

perror("socket:");

exit(1);

}

server_addr.sin_family = AF_INET;

server_addr.sin_port = htons(SERVPORT);

inet_pton(AF_INET, argv[1], &server_addr.sin_addr);

memset(&(server_addr.sin_zero), 0, 8);

/* create the connection by socket

* means that connect "sockfd" to "server_addr"

*/

if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)

{

perror("connect");

exit(1);

}

/**/

if (send(sockfd, snd_buf, sizeof(snd_buf), 0) == -1)

{

perror("send:");

exit(1);

}

printf("send:%s\n", snd_buf);

while (1)

{

FD_ZERO(&readset); //每次循环都要清空集合，否则不能检测描述符变化

FD_SET(sockfd, &readset); //添加描述符

FD_ZERO(&writeset);

FD_SET(fp, &writeset);

maxfd = sockfd > fp ? (sockfd+1) : (fp+1); //描述符最大值加1

ret = select(maxfd, &readset, NULL, NULL,
&timeout); // 非阻塞模式

switch( ret)

{

case -1:

exit(-1);

break;

case 0:

break;

default:

if (FD_ISSET(sockfd, &readset)) //测试sock是否可读，即是否网络上有数据

{

recvbytes = recv(sockfd, rcv_buf, MAXDATASIZE, MSG_DONTWAIT);

rcv_buf[recvbytes] = '\0';

printf("recv:%s\n", rcv_buf);

if (FD_ISSET(fp, &writeset))

{

write(fp, rcv_buf, strlen(rcv_buf)); // 不是用fwrite

}

goto end;

}

}

timeout.tv_sec = check_timeval; // 必须重新设置，因为超时时间到后会将其置零

cir_count++;

printf("CNT : %d \n",cir_count);

}

end:

close(fp);

close(sockfd);

return 0;

}

五、server端程序:

/*

* \brief

* tcp server

*/

#include <stdio.h>

#include <sys/socket.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <string.h>

#include <stdlib.h>

#define SERVPORT 8080

#define BACKLOG 10 // max numbef of client connection

#define MAXDATASIZE 100

int main(char argc, char *argv[])

{

int sockfd, client_fd, addr_size, recvbytes;

char rcv_buf[MAXDATASIZE], snd_buf[MAXDATASIZE];

char* val;

struct sockaddr_in server_addr;

struct sockaddr_in client_addr;

int bReuseaddr = 1;

char IPdotdec[20];

/* create a new socket and regiter it to os .

* SOCK_STREAM means that supply tcp service,

* and must connect() before data transfort.

*/

if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)

{

perror("socket:");

exit(1);

}

/* setting server's socket */

server_addr.sin_family = AF_INET; // IPv4 network protocol

server_addr.sin_port = htons(SERVPORT);

server_addr.sin_addr.s_addr = INADDR_ANY; // auto IP detect

memset(&(server_addr.sin_zero),0, 8);

setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (const char*)&bReuseaddr, sizeof(int));

if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(struct sockaddr))== -1)

{

perror("bind:");

exit(1);

}

/*

* watting for connection ,

* and server permit to recive the requestion from sockfd

*/

if (listen(sockfd, BACKLOG) == -1) // BACKLOG assign thd max number of connection

{

perror("listen:");

exit(1);

}



while(1)

{

addr_size = sizeof(struct sockaddr_in);



/*

* accept the sockfd's connection,

* return an new socket and assign far host to client_addr

*/

printf("watting for connect...\n");

if ((client_fd = accept(sockfd, (struct sockaddr *)&client_addr, &addr_size)) == -1)

{

/* Nonblocking mode */

perror("accept:");

continue;

}



/* network-digital to ip address */

inet_ntop(AF_INET, (void*)&client_addr, IPdotdec, 16);

printf("connetion from:%d : %s\n",client_addr.sin_addr, IPdotdec);



//if (!fork())

{

/* child process handle with the client connection */



/* recive the client's data by client_fd */

if ((recvbytes = recv(client_fd, rcv_buf, MAXDATASIZE, 0)) == -1)

{

perror("recv:");

exit(1);

}

rcv_buf[recvbytes]='\0';

printf("recv:%s\n", rcv_buf);





*snd_buf='\0';

strcat(snd_buf, "welcome");



sleep(3);

/* send the message to far-hosts by client_fd */

if (send(client_fd, snd_buf, strlen(snd_buf), 0) == -1)

{

perror("send:");

exit(1);

}

printf("send:%s\n", snd_buf);



close(client_fd);

//exit(1);

}



//close(client_fd);

}

return 0;

}

九四，或跃在渊，无咎。

【白话】九四，龙或腾跃而起，或退居于渊，均不会有危害。

《象》曰：“或跃在渊”，进无咎也。

【白话】《象辞》说：“龙或腾跃而起，或退居于渊，均不会有危害”，因为能审时度势，故进退自如，不会有危害。

转自：http://blog.chinaunix.net/uid-26000296-id-3755268.html