golang判斷tcp是否斷開的方法：

keepalive檢測，對于設(shè)置了keepalive來說，當(dāng)tcp檢測到對端socket不再可用時(shí)(不能發(fā)出探測包,或探測包沒有收到ACK的響應(yīng)包),select會返回socket可讀,并且在recv時(shí)返回-1,同時(shí)置上errno為ETIMEDOUT。此時(shí)TCP的狀態(tài)是斷開的。

struct TCP_KEEPALIVE {       unsigned long onoff;       unsigned long keepalivetime;       unsigned long keepaliveinterval;   } ;      #define SIO_KEEPALIVE_VALS _WSAIOW(IOC_VENDOR,4)      /* KeepAlive實(shí)現(xiàn) */   void set_keepalive (SOCKET s)   {       BOOL bKeepAlive = TRUE;       int nRet = ::setsockopt(s, SOL_SOCKET, SO_KEEPALIVE, (char*)&bKeepAlive, sizeof(bKeepAlive));       if (nRet == SOCKET_ERROR)       {           return ;       }       /* 輸入?yún)?shù) */       struct TCP_KEEPALIVE inKeepAlive = {0};        unsigned long ulInLen = sizeof(struct TCP_KEEPALIVE);          /* 輸出參數(shù) */       struct TCP_KEEPALIVE outKeepAlive = {0};        unsigned long ulOutLen = sizeof(struct TCP_KEEPALIVE);       unsigned long ulBytesReturn = 0;       int ret = 0;          /* 設(shè)置keepalive 為5秒，并且發(fā)送次數(shù)為3次 */       inKeepAlive.onoff             = 1;       /* 2次keepalive探測間隔時(shí)間 */       inKeepAlive.keepaliveinterval = 5000;        /* 開始首次keepalive探測前的tcp空閑時(shí)間 */       inKeepAlive.keepalivetime     = 5000;           ret = WSAIoctl((unsigned int)s,               SIO_KEEPALIVE_VALS,               (LPVOID)&inKeepAlive,                ulInLen,               (LPVOID)&outKeepAlive,                ulOutLen,               &ulBytesReturn,                NULL,                NULL);       if (ret == SOCKET_ERROR)       {           printf ("error: %dn", WSAGetLastError());       }   }