2 ACE Socket封装器
这部分内容不是ACE的网络框架,而是ACE对Socket API的面向对象的封装,在ACE中称为Socket Wrapper Facade。它是ACE网络框架的基础。
ACE将Socket应用接口封装到3个不同的类中,它们是ACE_SOCK_Stream、ACE_SOCK_Acceptor和ACE_SOCK_Connector,结构如图2-1所示。
图2-1 Socket封装器结构图
其中:
- ACE_SOCK_Stream 表示一条由通信双方建立的通信流,它之进行I/O操作,需要一个Socket描述符,保存在ACE_IPC_SAP类的数据成员handle_中。
- ACE_SOCK_Connector只进行主动连接操作,连接的Socket描述符保存在ACE_SOCK_Stream中。每一个连接都有一个ACE_SOCK_Stream对象,用于后续的I/O操作。
- ACE_SOCK_Acceptor只用于被动连接。被动连接需要一个侦听的Scoket描述符,同样也保存在ACE_IPC_SAP类的handle_中。
2.1 Socket IPC分析
进程间通信(IPC)是操作系统提供的一个非常重要的功能。进程间通信的方式非常多,如用于远程通信的Socket接口、TLI接口,用于本机通信的SVR4 STREAM管道、UNIX FIFO、Windows命名管道等。为了将这些不同的进程间通信方式封装成面向对象的接口,ACE设计了一个IPC Wrapper Facader组件,用于简化通信软件的开发。而ACE_IPC_SAP类是ACE IPC Wrapper Facader继承结构的根基类。其实ACE_IPC_SAP类除了图2-1中的ACE_SOCK类、ACE_FIFO类外,还有ACE_SPIPE、ACE_TLI等其他类,它们都用于不同形式的进程间通信。
ACE_IPC_SAP类主要有两个功能:一个是包含一个数据成员handle_,用于保存文件描述符;另一个是提供成员函数用于基本的I/O属性操作。ACE_IPC_SAP类代码清单如下:
// 代码在ace/IPC_SAP.h文件中
#ifndef ACE_IPC_SAP_H
#define ACE_IPC_SAP_H
#include /**/ "ace/pre.h"
#include "ace/Flag_Manip.h"
#include "ace/os_include/sys/os_types.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
class ACE_Export ACE_IPC_SAP
{
public:
/// Interface for <ioctl>.
int control (int cmd, void *) const;
// = Common I/O handle options related to sockets.
/**
* Enable asynchronous I/O (ACE_SIGIO), urgent data (ACE_SIGURG),
* non-blocking I/O (ACE_NONBLOCK), or close-on-exec (ACE_CLOEXEC),
* which is passed as the @a value.
*/
int enable (int value) const;
/**
* Disable asynchronous I/O (ACE_SIGIO), urgent data (ACE_SIGURG),
* non-blocking I/O (ACE_NONBLOCK), or close-on-exec (ACE_CLOEXEC),
* which is passed as the @a value.
*/
int disable (int value) const;
/// Get the underlying handle.
ACE_HANDLE get_handle (void) const;
/// Set the underlying handle.
void set_handle (ACE_HANDLE handle);
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
// = Ensure that ACE_IPC_SAP is an abstract base class.
/// Default constructor.
ACE_IPC_SAP (void);
/// Protected destructor.
/**
* Not a virtual destructor. Protected destructor to prevent
* operator delete() from being called through a base class
* ACE_IPC_SAP pointer/reference.
*/
~ACE_IPC_SAP (void);
private:
/// Underlying I/O handle. handle_是I/O操作的文件描述符
ACE_HANDLE handle_;
/// Cache the process ID. pid_用于保存进程号
static pid_t pid_;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/IPC_SAP.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* ACE_IPC_SAP_H */
(1)ACE_IPC_SAP类的构造函数和析构函数都是protected类型的。这样可以防止ACE_IPC_SAP被直接实例化,使它可以成为一个抽象类。
(2)ACE_IPC_SAP类用两个重要的函数:enable函数和disable函数,用于设置和取消描述符的属性。由于它们完全属于文件属性操作。
(3)ACE_SOCK是ACE_IPC_SAP类的子类,用于实现基于Socket接口的通信方式。它的主要功能是创建Socket和设置Socket属性。ACE_SOCK类的open函数用于创建Socket,并且将描述符保存在父类的handle_数据成员中。open函数有两种重置的形式,以适应不同的平台,代码清单如下:
// 代码在ace/SOCK.h中
/// Wrapper around the BSD-style @c socket system call (no QoS).
int open (int type,
int protocol_family,
int protocol,
int reuse_addr);
/// Wrapper around the QoS-enabled @c WSASocket function.
int open (int type,
int protocol_family,
int protocol,
ACE_Protocol_Info *protocolinfo,
ACE_SOCK_GROUP g,
u_long flags,
int reuse_addr);
2.2 ACE_SOCK_Acceptor类的分析
ACE_SOCK_Acceptor类用于被动连接端,它的作用是建立侦听Socket,等待客户端的连接。应用程序通过open函数建立侦听的Socket,通过accept函数等待客户端的连接。ACE_SOCK_Acceptor类的代码清单如下:
// 代码在ace/SOCK_Acceptor.h中
#ifndef ACE_SOCK_ACCEPTOR_H
#define ACE_SOCK_ACCEPTOR_H
#include /**/ "ace/pre.h"
#include "ace/SOCK_Stream.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
class ACE_Time_Value;
class ACE_Accept_QoS_Params;
class ACE_Export ACE_SOCK_Acceptor : public ACE_SOCK
{
public:
// = Initialization and termination methods.
/// Default constructor.
ACE_SOCK_Acceptor (void);
/**
* Initialize a passive-mode BSD-style acceptor socket (no QoS).
* @a local_sap is the address that we're going to listen for
* connections on. If @a reuse_addr is 1 then we'll use the
* @c SO_REUSEADDR to reuse this address.
*/
ACE_SOCK_Acceptor (const ACE_Addr &local_sap,
int reuse_addr = 0,
int protocol_family = PF_UNSPEC,
int backlog = ACE_DEFAULT_BACKLOG,
int protocol = 0);
/// Initialize a passive-mode QoS-enabled acceptor socket. Returns 0
/// on success and -1 on failure.
ACE_SOCK_Acceptor (const ACE_Addr &local_sap,
ACE_Protocol_Info *protocolinfo,
ACE_SOCK_GROUP g,
u_long flags,
int reuse_addr,
int protocol_family = PF_UNSPEC,
int backlog = ACE_DEFAULT_BACKLOG,
int protocol = 0);
/**
* Initialize a passive-mode BSD-style acceptor socket (no QoS).
* @a local_sap is the address that we're going to listen for
* connections on. If @a reuse_addr is 1 then we'll use the
* @c SO_REUSEADDR to reuse this address. Returns 0 on success and
* -1 on failure.
*/
int open (const ACE_Addr &local_sap,
int reuse_addr = 0,
int protocol_family = PF_UNSPEC,
int backlog = ACE_DEFAULT_BACKLOG,
int protocol = 0);
/// Initialize a passive-mode QoS-enabled acceptor socket. Returns 0
/// on success and -1 on failure.
int open (const ACE_Addr &local_sap,
ACE_Protocol_Info *protocolinfo,
ACE_SOCK_GROUP g,
u_long flags,
int reuse_addr,
int protocol_family = PF_UNSPEC,
int backlog = ACE_DEFAULT_BACKLOG,
int protocol = 0);
/// Close the socket. Returns 0 on success and -1 on failure.
int close (void);
/// Default dtor.
~ACE_SOCK_Acceptor (void);
// = Passive connection <accept> methods.
/**
* Accept a new ACE_SOCK_Stream connection. A @a timeout of 0
* means block forever, a @a timeout of {0, 0} means poll. @a restart
* == true means "restart if interrupted," i.e., if errno == EINTR.
* Note that @a new_stream inherits the "blocking mode" of @c this
* ACE_SOCK_Acceptor, i.e., if @c this acceptor factory is in
* non-blocking mode, the @a new_stream will be in non-blocking mode
* and vice versa.
*/
int accept (ACE_SOCK_Stream &new_stream,
ACE_Addr *remote_addr = 0,
ACE_Time_Value *timeout = 0,
bool restart = true,
bool reset_new_handle = false) const;
#if !defined (ACE_HAS_WINCE)
/**
* Accept a new ACE_SOCK_Stream connection using the QoS
* information in @a qos_params. A @a timeout of 0 means block
* forever, a @a timeout of {0, 0} means poll. @a restart == true means
* "restart if interrupted," i.e., if errno == EINTR. Note that
* @a new_stream inherits the "blocking mode" of @c this
* ACE_SOCK_Acceptor, i.e., if @c this acceptor factory is in
* non-blocking mode, the @a new_stream will be in non-blocking mode
* and vice versa.
*/
int accept (ACE_SOCK_Stream &new_stream,
ACE_Accept_QoS_Params qos_params,
ACE_Addr *remote_addr = 0,
ACE_Time_Value *timeout = 0,
bool restart = true,
bool reset_new_handle = false) const;
#endif // ACE_HAS_WINCE
// = Meta-type info
typedef ACE_INET_Addr PEER_ADDR;
typedef ACE_SOCK_Stream PEER_STREAM;
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
/// Perform operations that must occur before <ACE_OS::accept> is
/// called.
int shared_accept_start (ACE_Time_Value *timeout,
bool restart,
int &in_blocking_mode) const;
/// Perform operations that must occur after <ACE_OS::accept> is
/// called.
int shared_accept_finish (ACE_SOCK_Stream new_stream,
int in_blocking_mode,
bool reset_new_handle) const;
/**
* This method factors out the common <open> code and is called by
* both the QoS-enabled <open> method and the BSD-style <open>
* method.
*/
int shared_open (const ACE_Addr &local_sap,
int protocol_family,
int backlog);
private:
/// Do not allow this function to percolate up to this interface...
int get_remote_addr (ACE_Addr &) const;
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/SOCK_Acceptor.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* ACE_SOCK_ACCEPTOR_H */
(1)open函数
open函数用于建立一个侦听的Socket。它将Socket编程中的多个接口绑定在一个函数中,为应用程序隐藏了Socket编程的细节。
(2)accept函数
accept函数被应用程序调用,用来等待和接收客户端的连接。
(3)close函数
如果应用程序明确要关闭侦听的Socket,可以调用close()函数。ACE_SOCK_Stream、ACE_SOCK_Acceptor等类中,它们的析构函数都是空函数,而文件的关闭则必须放在close函数中。这是ACE的一种设计方式,只有应用程序明确调用close函数才关闭文件,这样可以避免在析构函数中出现自动关闭的情况。
2.3 ACE_SOCK_Connector类的分析
ACE_SOCK_Connector类用于客户端发起一个新连接,它的结构和ACE_SOCK_Acceptor非常相似。ACE_SOCK_Connector没有关闭函数,它的析构函数也为空,因为新连接的Socket句柄保存在ACE_SOCK_Stream对象中,由它负责关闭。
ACE_SOCK_Connector类只负责connect操作。
// 代码在ace/SOCK_Connector.h
#ifndef ACE_SOCK_CONNECTOR_H
#define ACE_SOCK_CONNECTOR_H
#include /**/ "ace/pre.h"
#include "ace/SOCK_Stream.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
ACE_BEGIN_VERSIONED_NAMESPACE_DECL
class ACE_QoS_Params;
class ACE_Time_Value;
/**
* @class ACE_SOCK_Connector
*
* @brief Defines a factory that actively connects to a remote IP
* address and TCP port, creating a new @c ACE_SOCK_Stream object.
*
* The @c ACE_SOCK_Connector doesn't have a socket of its own,
* i.e., it simply "borrows" the one from the @c ACE_SOCK_Stream
* that's being connected. The reason for this is that the
* underlying socket API doesn't use a factory socket to connect
* data mode sockets. Therefore, there's no need to inherit
* @c ACE_SOCK_Connector from @c ACE_SOCK. A nice side-effect of
* this is that @c ACE_SOCK_Connector objects do not store state so
* they can be used reentrantly in multithreaded programs.
*/
class ACE_Export ACE_SOCK_Connector
{
public:
/// Default constructor.
ACE_SOCK_Connector (void);
/**
* Actively connect to a peer, producing a connected @c ACE_SOCK_Stream
* object if the connection succeeds.
*
* @param new_stream The @c ACE_SOCK_Stream object that will be connected
* to the peer.
* @param remote_sap The address that we are trying to connect to.
* The protocol family of @c remote_sap is used for
* the connected socket. That is, if @c remote_sap
* contains an IPv6 address, a socket with family
* PF_INET6 will be used, else it will be PF_INET.
* @param timeout Pointer to an @c ACE_Time_Value object with amount
* of time to wait to connect. If the pointer is 0
* then the call blocks until the connection attempt
* is complete, whether it succeeds or fails. If
* *timeout == {0, 0} then the connection is done
* using nonblocking mode. In this case, if the
* connection can't be made immediately, this method
* returns -1 and errno == EWOULDBLOCK.
* If *timeout > {0, 0} then this is the maximum amount
* of time to wait before timing out; if the specified
* amount of time passes before the connection is made,
* this method returns -1 and errno == ETIME. Note
* the difference between this case and when a blocking
* connect is attempted that TCP times out - in the latter
* case, errno will be ETIMEDOUT.
* @param local_sap (optional) The local address to bind to. If it's
* the default value of @c ACE_Addr::sap_any then the
* OS will choose an unused port.
* @param reuse_addr (optional) If the value is 1, the local address
* (@c local_sap) is reused, even if it hasn't been
* cleaned up yet.
* @param flags Ignored.
* @param perms Ignored.
* @param protocol (optional) If value is 0, default SOCK_STREAM
* protocol is selected by kernel (typically TCP).
*/
ACE_SOCK_Connector (ACE_SOCK_Stream &new_stream,
const ACE_Addr &remote_sap,
const ACE_Time_Value *timeout = 0,
const ACE_Addr &local_sap = ACE_Addr::sap_any,
int reuse_addr = 0,
int flags = 0,
int perms = 0,
int protocol = 0);
#if !defined (ACE_HAS_WINCE)
/**
* Actively connect to a peer, producing a connected @c ACE_SOCK_Stream
* object if the connection succeeds.
*
* @param new_stream The @c ACE_SOCK_Stream object that will be connected
* to the peer.
* @param remote_sap The address that we are trying to connect to.
* The protocol family of @c remote_sap is used for
* the connected socket. That is, if @c remote_sap
* contains an IPv6 address, a socket with family
* PF_INET6 will be used, else it will be PF_INET.
* @param qos_params Contains QoS parameters that are passed to the
* IntServ (RSVP) and DiffServ protocols.
* @see ACE_QoS_Params.
* @param timeout Pointer to an @c ACE_Time_Value object with amount
* of time to wait to connect. If the pointer is 0
* then the call blocks until the connection attempt
* is complete, whether it succeeds or fails. If
* *timeout == {0, 0} then the connection is done
* using nonblocking mode. In this case, if the
* connection can't be made immediately, this method
* returns -1 and errno == EWOULDBLOCK.
* If *timeout > {0, 0} then this is the maximum amount
* of time to wait before timing out; if the specified
* amount of time passes before the connection is made,
* this method returns -1 and errno == ETIME. Note
* the difference between this case and when a blocking
* connect is attempted that TCP times out - in the latter
* case, errno will be ETIMEDOUT.
* @param local_sap (optional) The local address to bind to. If it's
* the default value of @c ACE_Addr::sap_any then the
* OS will choose an unused port.
* @param reuse_addr (optional) If the value is 1, the local address
* (@c local_sap) is reused, even if it hasn't been
* cleaned up yet.
* @param flags Ignored.
* @param perms Ignored.
*/
ACE_SOCK_Connector (ACE_SOCK_Stream &new_stream,
const ACE_Addr &remote_sap,
ACE_QoS_Params qos_params,
const ACE_Time_Value *timeout = 0,
const ACE_Addr &local_sap = ACE_Addr::sap_any,
ACE_Protocol_Info *protocolinfo = 0,
ACE_SOCK_GROUP g = 0,
u_long flags = 0,
int reuse_addr = 0,
int perms = 0);
#endif // ACE_HAS_WINCE
/**
* Actively connect to a peer, producing a connected @c ACE_SOCK_Stream
* object if the connection succeeds.
*
* @param new_stream The @c ACE_SOCK_Stream object that will be connected
* to the peer.
* @param remote_sap The address that we are trying to connect to.
* The protocol family of @c remote_sap is used for
* the connected socket. That is, if @c remote_sap
* contains an IPv6 address, a socket with family
* PF_INET6 will be used, else it will be PF_INET.
* @param timeout Pointer to an @c ACE_Time_Value object with amount
* of time to wait to connect. If the pointer is 0
* then the call blocks until the connection attempt
* is complete, whether it succeeds or fails. If
* *timeout == {0, 0} then the connection is done
* using nonblocking mode. In this case, if the
* connection can't be made immediately, this method
* returns -1 and errno == EWOULDBLOCK.
* If *timeout > {0, 0} then this is the maximum amount
* of time to wait before timing out; if the specified
* amount of time passes before the connection is made,
* this method returns -1 and errno == ETIME. Note
* the difference between this case and when a blocking
* connect is attempted that TCP times out - in the latter
* case, errno will be ETIMEDOUT.
* @param local_sap (optional) The local address to bind to. If it's
* the default value of @c ACE_Addr::sap_any then the
* OS will choose an unused port.
* @param reuse_addr (optional) If the value is 1, the local address
* (@c local_sap) is reused, even if it hasn't been
* cleaned up yet.
* @param flags Ignored.
* @param perms Ignored.
* @param protocol (optional) If value is 0, default SOCK_STREAM
* protocol is selected by kernel (typically TCP).
*
* @return Returns 0 if the connection succeeds. If it fails,
* -1 is returned and errno contains a specific error
* code.
*/
int connect (ACE_SOCK_Stream &new_stream,
const ACE_Addr &remote_sap,
const ACE_Time_Value *timeout = 0,
const ACE_Addr &local_sap = ACE_Addr::sap_any,
int reuse_addr = 0,
int flags = 0,
int perms = 0,
int protocol = 0);
#if !defined (ACE_HAS_WINCE)
/**
* Actively connect to a peer, producing a connected @c ACE_SOCK_Stream
* object if the connection succeeds.
*
* @param new_stream The @c ACE_SOCK_Stream object that will be connected
* to the peer.
* @param remote_sap The address that we are trying to connect to.
* The protocol family of @c remote_sap is used for
* the connected socket. That is, if @c remote_sap
* contains an IPv6 address, a socket with family
* PF_INET6 will be used, else it will be PF_INET.
* @param qos_params Contains QoS parameters that are passed to the
* IntServ (RSVP) and DiffServ protocols.
* @see ACE_QoS_Params.
* @param timeout Pointer to an @c ACE_Time_Value object with amount
* of time to wait to connect. If the pointer is 0
* then the call blocks until the connection attempt
* is complete, whether it succeeds or fails. If
* *timeout == {0, 0} then the connection is done
* using nonblocking mode. In this case, if the
* connection can't be made immediately, this method
* returns -1 and errno == EWOULDBLOCK.
* If *timeout > {0, 0} then this is the maximum amount
* of time to wait before timing out; if the specified
* amount of time passes before the connection is made,
* this method returns -1 and errno == ETIME. Note
* the difference between this case and when a blocking
* connect is attempted that TCP times out - in the latter
* case, errno will be ETIMEDOUT.
* @param local_sap (optional) The local address to bind to. If it's
* the default value of @c ACE_Addr::sap_any then the
* OS will choose an unused port.
* @param reuse_addr (optional) If the value is 1, the local address
* (@c local_sap) is reused, even if it hasn't been
* cleaned up yet.
* @param flags Ignored.
* @param perms Ignored.
*
* @return Returns 0 if the connection succeeds. If it fails,
* -1 is returned and errno contains a specific error
* code.
*/
int connect (ACE_SOCK_Stream &new_stream,
const ACE_Addr &remote_sap,
ACE_QoS_Params qos_params,
const ACE_Time_Value *timeout = 0,
const ACE_Addr &local_sap = ACE_Addr::sap_any,
ACE_Protocol_Info *protocolinfo = 0,
ACE_SOCK_GROUP g = 0,
u_long flags = 0,
int reuse_addr = 0,
int perms = 0);
#endif // ACE_HAS_WINCE
/// Default destructor.
~ACE_SOCK_Connector (void);
// = Completion routine.
/**
* Try to complete a nonblocking connection that was begun by a
* previous call to connect with a {0, 0} ACE_Time_Value timeout.
* @see connect().
*
* @param new_stream The @c ACE_SOCK_Stream object that will be connected
* to the peer.
* @param remote_sap If non-0, it points to the @c ACE_INET_Addr object
* that will contain the address of the connected peer.
* @param timeout Same values and return value possibilites as for
* connect(). @see connect().
*/
int complete (ACE_SOCK_Stream &new_stream,
ACE_Addr *remote_sap = 0,
const ACE_Time_Value *timeout = 0);
/// Resets any event associations on this handle
bool reset_new_handle (ACE_HANDLE handle);
// = Meta-type info
typedef ACE_INET_Addr PEER_ADDR;
typedef ACE_SOCK_Stream PEER_STREAM;
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
protected:
/// Perform operations that ensure the socket is opened using
/// BSD-style semantics (no QoS).
int shared_open (ACE_SOCK_Stream &new_stream,
int protocol_family,
int protocol,
int reuse_addr);
/// Perform operations that ensure the socket is opened using
/// QoS-enabled semantics.
int shared_open (ACE_SOCK_Stream &new_stream,
int protocol_family,
int protocol,
ACE_Protocol_Info *protocolinfo,
ACE_SOCK_GROUP g,
u_long flags,
int reuse_addr);
/// Perform operations that must be called before <ACE_OS::connect>.
int shared_connect_start (ACE_SOCK_Stream &new_stream,
const ACE_Time_Value *timeout,
const ACE_Addr &local_sap);
/// Perform operations that must be called after <ACE_OS::connect>.
int shared_connect_finish (ACE_SOCK_Stream &new_stream,
const ACE_Time_Value *timeout,
int result);
};
ACE_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "ace/SOCK_Connector.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* ACE_SOCK_CONNECTOR_H */
【源码并没有仔细看看,就是粗粗的浏览了一下,网络编程的基础不牢靠,还是有些看不懂。先记录下来,做一个学习的标记。】
参考文献:
[1] ACE技术内幕:深入解析ACE架构设计与实现原理