注:这一片博客与下一篇博客<Socket编程实践(20)>合为一篇,由于代码较多,所以分为两篇,本篇为上篇,主要讲解前一篇讲解的Socket类的增强,下一篇主要讲解怎样使用这个增强版的Socket类(ServerSocket/ClientSocket类的实现与使用)!

思想来源:

    1)http://www.cnblogs.com/-Lei/archive/2012/09/04/2670964.html

    2)http://blog.csdn.net/column/details/linux66.html

    3)http://blog.csdn.net/column/details/zjf666.html

修改内容:

    1)修改了Socket类几个成员函数的访问权限(由public改为protected, 使Socket类可以进行继承,但不允许私自使用)

    2)添加了Close, getAddr, getPort成员函数,使得使用更方便(在下一节的server端代码中可以看到)

    3)Send/Receive函数该用著名的writen/readn实现(以前使用的是read/write系统调用),加强了Socket类的容错性.

    4)添加了异常处理,让我们在编写易出错的代码时,可以解放思想,不用一直考虑该函数调用出错会发生什么情况!

Socket.h

#ifndef SOCKET_H_INCLUDED
#define SOCKET_H_INCLUDED

#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string>
#include <string.h>
#include <fcntl.h>

class Socket
{
public:
    Socket();
    virtual ~Socket();  //virtual destructior

//Protect The Function, Only Used to Server Or Client
protected:
    bool Create(); //Create a socket, server & client can use

    /**Server**/
    bool Bind(int port) const;  //Bind a port
    bool Listen(int backlog = SOMAXCONN) const; //Start to listen
    bool Accept(Socket& clientSocket) const;    //Accept a connect

    /**Client**/
    bool Connect(const std::string& host, int port);


    /** Data Transmission:
        return=0: write or read nothing (if receive == 0,peer connect closed)
        return<0: write error(errno is set)
        return>0: write success(return value is the bytes have send/receive)
    **/
    size_t Send(const Socket& socket, const std::string& message) const;
    size_t Receive(const Socket& socket, std::string& message) const;

public:
    /***All can Use!***/

    //flag: true=SetNonBlock, false=SetBlock
    bool SetNonBlocking(bool flag);

    //return: true -> SetSuccess
    bool SetReuseAddr();

    //test for m_sockfd;
    bool IsValid() const;
    //close the socket
    bool Close();

public:
    std::string getAddr();
    int getPort() const;

private:
    //use m_sockfd to record the result of function socket
    int m_sockfd;
    struct sockaddr_in m_address;
    //define the max bytes to send/write
    static const int BUFSIZ = 1024*10;
};

#endif // SOCKET_H_INCLUDED

Socket.cpp

#include "Socket.h"

static ssize_t readn(int fd, void *buf, size_t count);
static ssize_t writen(int fd, const void *buf, size_t count);

Socket::Socket():m_sockfd(-1)
{
}
Socket::~Socket()
{
    if (IsValid())
    {
        close(m_sockfd);
    }
}

bool Socket::Close()
{
    if (IsValid())
    {
        ::close(m_sockfd);
        m_sockfd = -1;
        return true;
    }
    return false;
}

bool Socket::Create()
{
    m_sockfd = socket(AF_INET,SOCK_STREAM,0);
    if (IsValid())
        return true;
    return false;
}

//bind a server port at the server
bool Socket::Bind(int port) const
{
    if (!IsValid())
    {
        return false;
    }

    struct sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(port);
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(m_sockfd,(const struct sockaddr *)&serverAddr,
             sizeof(struct sockaddr)) == -1)
    {
        return false;
    }
    return true;
}

bool Socket::Listen(int backlog) const
{
    if (!IsValid())
    {
        return false;
    }

    if (listen(m_sockfd,backlog) == -1)
    {
        return false;
    }
    return true;
}

bool Socket::Accept(Socket &clientSocket) const
{
    if (!IsValid())
    {
        return false;
    }

    socklen_t clientAddrLength = sizeof(clientSocket.m_address);
    clientSocket.m_sockfd = accept(m_sockfd, (struct sockaddr *)(&clientSocket.m_address),
                                   &clientAddrLength);
    if (clientSocket.m_sockfd == -1)
    {
        return false;
    }
    return true;
}

//Client
bool Socket::Connect(const std::string &serverHost, int serverPort)
{
    if (!IsValid())
    {
        return false;
    }

    struct sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr(serverHost.c_str());
    serverAddr.sin_port = htons(serverPort);

    if (connect(m_sockfd,(const struct sockaddr *)(&serverAddr),
                sizeof(struct sockaddr)) == -1)
    {
        return false;
    }

    return true;
}

size_t Socket::Send(const Socket &peerSocket, const std::string &messages) const
{

    struct TransStruct
    {
        size_t bufLen;      //保存真实的报文内容长度
        char buf[BUFSIZ];   //真正要发送的报文内容
    } sendStruct;

    sendStruct.bufLen = messages.length();
    strncpy(sendStruct.buf,messages.c_str(),sendStruct.bufLen);

    ssize_t nWrited = writen(peerSocket.m_sockfd,&sendStruct,
                            sendStruct.bufLen+sizeof(size_t));

    if (nWrited == 0)
    {
        return 0;
    }
    else if (nWrited == -1)
    {
        return -1;
    }

    return nWrited;
}

size_t Socket::Receive(const Socket &peerSocket, std::string &messages) const
{
    size_t messageLen = 0;
    if (readn(peerSocket.m_sockfd,&messageLen,sizeof(size_t)) == -1)
    {
        return false;
    }

    char buf[BUFSIZ];
    memset(buf,0,sizeof(buf));
    messages.clear();

    ssize_t nRead = readn(peerSocket.m_sockfd,buf,messageLen);
    if (nRead == 0)
    {
        return 0;
    }
    else if (nRead == -1)
    {
        return -1;
    }

    messages = buf;
    return nRead;
}

//Set the sockfd NonBlocked
bool Socket::SetNonBlocking(bool flag)
{
    if (IsValid())
    {
        int opts = fcntl(m_sockfd,F_GETFL);
        if (opts == -1)
        {
            return false;
        }

        if (flag)
        {
            opts |= O_NONBLOCK;
        }
        else
        {
            opts &= ~O_NONBLOCK;
        }

        return fcntl(m_sockfd,F_SETFL,opts);
    }

    return false;
}

//Set the address Reused
bool Socket::SetReuseAddr()
{
    if (IsValid())
    {
        int on = 1;
        if (setsockopt(m_sockfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on)) == -1)
        {
            return false;
        }
        else
        {
            return true;
        }
    }
    return false;
}

bool Socket::IsValid() const
{
    //If m_sockfd is not Call Create, m_sockfd == -1
    //Else m_sockfd != -1
    return m_sockfd != -1;
}

std::string Socket::getAddr()
{
    if (IsValid())
    {
        return inet_ntoa(m_address.sin_addr);
    }
    return std::string();
}
int Socket::getPort() const
{
    if (IsValid())
    {
        return ntohs(m_address.sin_port);
    }
    return -1;
}

static ssize_t readn(int fd, void *buf, size_t count)
{
    size_t nLeft = count;
    ssize_t nRead = 0;

    char *ptr = static_cast<char *>(buf);

    while (nLeft > 0)
    {
        if ((nRead = read(fd,ptr,nLeft)) < 0)
        {
            //nothing have read!!!
            if (nLeft == count)
            {
                return -1;  //error
            }
            else
            {
                break;  //error, return amount read so far
            }
        }
        else if (nRead == 0)
        {
            break;  //EOF
        }

        //continue to read
        nLeft -= nRead;
        ptr += nRead;
    }

    return count - nLeft;
}
static ssize_t writen(int fd, const void *buf, size_t count)
{
    size_t nLeft = count;
    ssize_t nWritten;

    const char *ptr = static_cast<const char *>(buf);

    while (nLeft > 0)
    {
        if ((nWritten = write(fd,ptr,nLeft)) < 0)
        {
            //nothing have write
            if (nLeft == count)
            {
                return -1;  //error
            }
            else
            {
                break;  //error, return amount write so far
            }
        }
        else if (nWritten == 0)
        {
            break;  //EOF
        }

        nLeft -= nWritten;
        ptr += nWritten;
    }

    return count - nWritten;
}

SocketException.h

#ifndef SOCKETEXCEPTION_H_INCLUDED
#define SOCKETEXCEPTION_H_INCLUDED

//异常处理类(下一节会用到...)
class SocketException
{
public:
    SocketException(const std::string &description):
        m_description(description){}
    ~SocketException(){}

    std::string Description()
    {
        return m_description;
    }

private:
    std::string m_description;
};


#endif // SOCKETEXCEPTION_H_INCLUDED

Socket编程实践(19) --Socket API封装(2)