比较在windows中以及Linux中设置keepalive
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作者：huzhangyou
Blog: http://doserver.net
QQ:3803308

windows中有一个结构体，叫做tcp_keepalive，我们通过WSAIoctl设置SIO_KEEPALIVE_VALS可以达到目的，函数的简写如下：
void SetKeepalive(int time){     const char chOpt = 1;     if (setsockopt(_client, SOL_SOCKET, SO_KEEPALIVE, (char *)&chOpt, sizeof(chOpt)) != 0)     { #ifdef _DEBUG       cout << "setsockopt() error\n" << WSAGetLastError() << endl; #endif     }     tcp_keepalive  klive;     klive.onoff = 1; // 启用保活     klive.keepalivetime = time;     klive.keepaliveinterval = 1000 * 10; // 重试间隔为10秒 Resend if No-Reply     WSAIoctl     (       _client,       SIO_KEEPALIVE_VALS,       &klive,       sizeof(tcp_keepalive),       NULL,       0,       (unsigned long *)&chOpt,       0,       NULL     );   }

而在Linux中，我们的方法有点不同，代码示意如下：
      if(!(env = getenv("KEEPALIVE")) || strcasecmp(env, "skip")) {         setsockopt(s, SOL_SOCKET, SO_KEEPALIVE, &optval, sizeof(optval));       } #ifdef TCP_KEEPCNT       if((env = getenv("KEEPCNT")) && ((optval = atoi(env)) >= 0)) {         setsockopt(s, SOL_TCP, TCP_KEEPCNT, &optval, sizeof(optval));       } #endif #ifdef TCP_KEEPIDLE       if((env = getenv("KEEPIDLE")) && ((optval = atoi(env)) >= 0)) {         setsockopt(s, SOL_TCP, TCP_KEEPIDLE, &optval, sizeof(optval));       } #endif #ifdef TCP_KEEPINTVL       if((env = getenv("KEEPINTVL")) && ((optval = atoi(env)) >= 0)) {         setsockopt(s, SOL_TCP, TCP_KEEPINTVL, &optval, sizeof(optval));       } #endif

上述代码一摘自我的IOCP 框架
代码二摘自http://libkeepalive.sourceforge.net/