linux下socket编程 select只监测读事件, 为什么还会出现读阻塞

Question

我用select监测读时间,但是read出现了阻塞

maxfd = iListenFdIP;
maxi = -1;
for(i=0 ; i<CONNCT_NUM_MAX; ++i)
{
    client[i][0] = -1;
}//for
FD_ZERO(&allset);
FD_SET(iListenFdIP , &allset);
i = 0;
while(1){
    rset = allset;
    nready = select(maxfd+1 , &rset , NULL , NULL , NULL);

// DEBUG(LOG_DEBUG,"nread:%d\n",nready);
if(FD_ISSET(iListenFdIP , &rset))
{
/*接收客户端的请求*/
clilen = sizeof(cliaddr);

// DEBUG(LOG_DEBUG,"\naccpet connection~\n");

        if((connfd = accept( iListenFdIP, (struct sockaddr *)&cliaddr , &clilen)) < 0)
        {
            DEBUG(LOG_ERROR,"accept error.\n");
            continue;
        }//if       

        DEBUG(LOG_DEBUG,"accpet a new client: %s:%d\n", inet_ntoa(cliaddr.sin_addr) , cliaddr.sin_port);

        /*将客户链接套接字描述符添加到数组*/
        for(i=0 ; i<CONNCT_NUM_MAX ; ++i)
        {
            if(client[i][0] < 0)
            {
                client[i][0] = connfd;
                client[i][1] = cliaddr.sin_port;
                break;
            }//if
        }//for

        if(CONNCT_NUM_MAX == i)
        {
            DEBUG(LOG_ERROR,"too many connection.\n");
        }//if
        else
        {
            FD_SET(connfd , &allset);
            if(connfd > maxfd)
                maxfd = connfd;
            if(i > maxi)
                maxi = i;
        }


        if(--nready < 0)
            continue;
    }//if

// DEBUG(LOG_DEBUG,"maxi:%d\n",maxi);
for(i=0; i<=maxi ; ++i)
{
memset(caBuff,0x0,sizeof(caBuff));
memset(sndBuff,0x0,sizeof(sndBuff));

memset(caSplitBuff,0x0,sizeof(caSplitBuff));

if((sockfd = client[i][0]) < 0)
continue;
if(FD_ISSET(sockfd , &rset))
{
/*处理客户请求*/
//DEBUG(LOG_DEBUG,"\nreading the socket~~~ \n");

            if((n = read(sockfd , caBuff , sizeof(caBuff))) <= 0)
            {
                DEBUG(LOG_DEBUG,"client[%d] is close\n",i);
                close(sockfd);
                FD_CLR(sockfd , &allset);
                client[i][0] = -1;
            }//if
            else{

                char* cpPosNow = caBuff;

                if ( NULL == (cpPos = strchr(cpPosNow, '\n'))){
                    DEBUG(LOG_ERROR,"data:%s  can't find '\n' \n",cpPosNow);
                    continue;
                }
                iPkgLen = cpPos - cpPosNow;
                memcpy(caSplitBuff, cpPosNow, iPkgLen);

                inet_aton(caSplitBuff,&addr.sin_addr);

                memset(caSplitBuff,0x0,sizeof(caSplitBuff));
                memcpy(&tmpIP,&addr.sin_addr,4);
                //tmpIP = htonl(tmpIP);
                memcpy(caSplitBuff,&tmpIP,4);
                if(NULL == (pIpMapHashNode = ipmap_hash_table_lookup((const unsigned char *)caSplitBuff))){
                    res = send(sockfd, "IPOFFLINE\n",strlen("IPOFFLINE\n") , 0);
                    if(res < 0){
                        close(sockfd);
                        FD_CLR(sockfd , &allset);
                        client[i][0] = -1;
                        DEBUG(LOG_DEBUG,"Send ERROR:Client is close,ErrorNum = %d, ErrorMsg = %s\n", errno, strerror(errno));
                    }
                }
                else{

                    DEBUG(LOG_DEBUG,"recv IPV4:%d.%d.%d.%d username:%s dstprot:%d\n",
                                        caSplitBuff[0],caSplitBuff[1],caSplitBuff[2],caSplitBuff[3],pIpMapHashNode->UserName,client[i][1]);
                    memcpy(sndBuff, pIpMapHashNode->UserName, strlen(pIpMapHashNode->UserName));
                    strcat(sndBuff,"\n");
                    res = send(sockfd, sndBuff, strlen(pIpMapHashNode->UserName)+1, 0);
                    if(res <=  0){
                        close(sockfd);
                        FD_CLR(sockfd , &allset);
                        client[i][0] = -1;
                        DEBUG(LOG_DEBUG,"ERROR:Send Client is close,ErrorNum = %d, ErrorMsg = %s\n", errno, strerror(errno));                           
                    }
                }
            }
            if(--nready <= 0)
                break;
        }
    }
 }
 close(iListenFdIP);
 return;     

Answer 1

要设置你的socket为非阻塞模式