[转]怎样及时检测出非正常断开的TCP连接

peakzhang

2006年11月09日 17:38

作者:在水一鱼(powercc@21cn.com) 此处的”非正常断开”指TCP连接不是以优雅的方式断开,如网线故障等物理链路的原因,还有突然主机断电等原因 有两种方法可以检测:1.TCP连接双方定时发握手消息 2.利用TCP协议栈中的KeepAlive探测 第二种方法简单可靠,只需对TCP连接两个Socket设定KeepAlive探测,所以本文只讲第二种方法在Linux,Window2000下的实现(在其它的平台上没有作进一步的测试) windows 2000平台下 //定义结构及宏 struct TCP_KEEPALIVE { u_longonoff; u_longkeepalivetime; u_longkeepaliveinterval; } ; #define SIO_KEEPALIVE_VALS _WSAIOW(IOC_VENDOR,4) //KeepAlive实现 TCP_KEEPALIVE inKeepAlive = {0}; //输入参数 unsigned long ulInLen = sizeof(TCP_KEEPALIVE); TCP_KEEPALIVE outKeepAlive = {0}; //输出参数 unsigned long ulOutLen = sizeof(TCP_KEEPALIVE); unsigned long ulBytesReturn = 0; //设置socket的keep alive为5秒，并且发送次数为3次 inKeepAlive.onoff = 1; inKeepAlive.keepaliveinterval = 5000; //两次KeepAlive探测间的时间间隔 inKeepAlive.keepalivetime = 5000; //开始首次KeepAlive探测前的TCP空闭时间 if (WSAIoctl((unsigned int)s, SIO_KEEPALIVE_VALS, (LPVOID)&inKeepAlive, ulInLen, (LPVOID)&outKeepAlive, ulOutLen, &ulBytesReturn, NULL, NULL) == SOCKET_ERROR) { ACE_DEBUG ((LM_INFO, ACE_TEXT ("(%P|%t) \WSAIoctl failed. error code(%d)!\n"),WSAGetLastError())); } Linux平台下 #include …… ////KeepAlive实现 //下面代码要求有ACE,如果没有包含ACE,则请把用到的ACE函数改成linux相应的接口 int keepAlive = 1;//设定KeepAlive int keepIdle = 5;//开始首次KeepAlive探测前的TCP空闭时间 int keepInterval = 5;//两次KeepAlive探测间的时间间隔 int keepCount = 3;//判定断开前的KeepAlive探测次数 if(setsockopt(s,SOL_SOCKET,SO_KEEPALIVE,(void*)&keepAlive,sizeof(keepAlive)) == -1) { ACE_DEBUG ((LM_INFO, ACE_TEXT ("(%P|%t) setsockopt SO_KEEPALIVE error!\n"))); } if(setsockopt(s,SOL_TCP,TCP_KEEPIDLE,(void *)&keepIdle,sizeof(keepIdle)) == -1) { ACE_DEBUG ((LM_INFO, ACE_TEXT ("(%P|%t) setsockopt TCP_KEEPIDLE error!\n"))); } if(setsockopt(s,SOL_TCP,TCP_KEEPINTVL,(void *)&keepInterval,sizeof(keepInterval)) == -1) { ACE_DEBUG ((LM_INFO, ACE_TEXT ("(%P|%t) setsockopt TCP_KEEPINTVL error!\n"))); } if(setsockopt(s,SOL_TCP,TCP_KEEPCNT,(void *)&keepCount,sizeof(keepCount)) == -1) { ACE_DEBUG ((LM_INFO, ACE_TEXT ("(%P|%t)setsockopt TCP_KEEPCNT error!\n")));