select读写

#include <iostream>
using namespace std;

#ifdef WINDOWS_SOCK
#include <WinSock2.h>
#pragma comment(lib, "ws2_32.lib")
#define socklen_t int
#else
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <fcntl.h>
#define SOCKET int
#define closesocket(a) close(a) 
#endif

#define  SOCK_COUNT 5

SOCKET initSock();

int main()
{

    SOCKET skListen = initSock();

    //select
    int maxfd = skListen;
    int conn_count = 0;
    SOCKET skAll[SOCK_COUNT] = {0};
    char sndbuf[1024];
    sndbuf[0] = ‘\0‘;


    fd_set fdsetr, fdsetw;
    FD_ZERO(&fdsetr);
    FD_ZERO(&fdsetw);
    FD_SET(skListen, &fdsetr);

    fd_set fdRead;
    fd_set fdWrite;

    sockaddr_in acceptAddr;
    socklen_t len = sizeof(acceptAddr);
    //该参数为空时，则为阻塞select了
    struct timeval timeout = {3,0};
    while(true)
    {
        fdRead = fdsetr;
        fdWrite = fdsetw;

        //参考unix网络编程卷1(第三版):第6章,每个参数介绍很详细
        int num = select(maxfd + 1, &fdRead, &fdWrite, 0, &timeout);
        if (num > 0)
        {
            for (int i=0; i<conn_count; i++)
            {
                //recv        
                if(FD_ISSET(skAll[i], &fdRead))
                {
                    char buf[1024];
                    int ir = recv(skAll[i], buf, 1024, 0);
                    if (ir == -1)
                    {
                        getpeername(skAll[i], (sockaddr*)&acceptAddr, &len);  
                        cout<<"diss conn IP:"<<inet_ntoa(acceptAddr.sin_addr)
                            <<",PORT:"<<ntohs(acceptAddr.sin_port)<<endl;

                        closesocket(skAll[i]);
                        FD_CLR(skAll[i], &fdsetr);
                        skAll[i] = 0;
                        conn_count--;
                    }
                    else if (ir == 0)
                    {
                        cout<<"0:disconnect"<<endl;

                        closesocket(skAll[i]);
                        FD_CLR(skAll[i], &fdsetr);
                        skAll[i] = 0;
                        conn_count--;
                    }
                    else
                    {
                        buf[ir]=‘\0‘;
                        cout<<buf<<endl;

                        //fdwrite
                        char snd[50] = "notify client";
                        memcpy(sndbuf, snd, strlen(snd)+1);
                        FD_SET(skAll[i], &fdsetw);
                    }
                }

                //write
                if (FD_ISSET(skAll[i], &fdWrite))
                {
                    int ilen = strlen(sndbuf);
                    if (ilen > 0)
                    {
                        int ret = send(skAll[i], sndbuf, ilen, 0);
                        if (ret > 0 )
                        {
                            cout<<"send :"<<ret<<endl;
                        }

                        //FD_CLR(skAll[i], &fdsetr);
                        //FD_CLR(skAll[i], &fdsetw);
                        //closesocket(skAll[i]);
                        //conn_count--;
                    }

                    sndbuf[0] = ‘\0‘;
                }
            }//end for

            //accept
            if (FD_ISSET(skListen, &fdRead))
            {
                SOCKET skClient = accept(skListen, (sockaddr*)&acceptAddr, &len);
                cout<<"conn IP:"<<inet_ntoa(acceptAddr.sin_addr)
                <<",PORT:"<<ntohs(acceptAddr.sin_port)<<endl;

                FD_SET(skClient, &fdsetr);
                maxfd = skListen > skClient ? skListen : skClient;

                if (conn_count >= SOCK_COUNT)
                {
                    cout<<"max conn limit"<<endl;
                    closesocket(skClient);
                }
                else
                {

                int tmp = conn_count;
                do    
                {
                    if(skAll[tmp] == 0)
                    {
                        skAll[conn_count++] = skClient;
                        break;
                    }
                    tmp++;

                    if (tmp== SOCK_COUNT)
                    {
                        tmp= 0;
                    }
                }while(conn_count != tmp);
                }
            }

        }
    }

    system("pause");
    return 0;
}


SOCKET initSock()
{
#ifdef WINDOWS_SOCK
    //1.init        
    WSADATA wsa;
    if (WSAStartup(MAKEWORD(2,2), &wsa))
    {
        cout<<"1"<<endl;
    }
#endif

    //2.socket
    SOCKET skListen = socket(AF_INET, SOCK_STREAM, 0);

    //3.bind
    sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8080);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    bind(skListen, (sockaddr*)&addr, sizeof(addr));

    //4.listen
    listen(skListen, 5);

    return skListen;
}