[英]Socket keepalive not working
我有一個客戶端connect()到服務器,當空閑時,它會在幾個小時后超時。 我在1秒內添加了setsockopt(套接字,SOL_SOCKET,SO_KEEPALIVE ...),但它並沒有什么區別。 為什么keepalive不起作用的任何線索? 如果我使用SOL_TCP而不是SOL_SOCKET會有所不同嗎? 這是在Linux上。
int val = 1;
setsockopt(socket, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof val)
只需啟用Keepalive。 您將獲得keepalive探針的默認計時器,您可以使用以下命令查看:
sysctl net.ipv4.tcp_keepalive_time
通常默認值是幾個小時。
如果要更改默認計時器,可以使用:
struct KeepConfig cfg = { 60, 5, 5};
set_tcp_keepalive_cfg(fd, &cfg);
這里有輔助函數:
struct KeepConfig {
/** The time (in seconds) the connection needs to remain
* idle before TCP starts sending keepalive probes (TCP_KEEPIDLE socket option)
*/
int keepidle;
/** The maximum number of keepalive probes TCP should
* send before dropping the connection. (TCP_KEEPCNT socket option)
*/
int keepcnt;
/** The time (in seconds) between individual keepalive probes.
* (TCP_KEEPINTVL socket option)
*/
int keepintvl;
};
/**
* enable TCP keepalive on the socket
* @param fd file descriptor
* @return 0 on success -1 on failure
*/
int set_tcp_keepalive(int sockfd)
{
int optval = 1;
return setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &optval, sizeof(optval));
}
/** Set the keepalive options on the socket
* This also enables TCP keepalive on the socket
*
* @param fd file descriptor
* @param fd file descriptor
* @return 0 on success -1 on failure
*/
int set_tcp_keepalive_cfg(int sockfd, const struct KeepConfig *cfg)
{
int rc;
//first turn on keepalive
rc = set_tcp_keepalive(sockfd);
if (rc != 0) {
return rc;
}
//set the keepalive options
rc = setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPCNT, &cfg->keepcnt, sizeof cfg->keepcnt);
if (rc != 0) {
return rc;
}
rc = setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPIDLE, &cfg->keepidle, sizeof cfg->keepidle);
if (rc != 0) {
return rc;
}
rc = setsockopt(sockfd, IPPROTO_TCP, TCP_KEEPINTVL, &cfg->keepintvl, sizeof cfg->keepintvl);
if (rc != 0) {
return rc;
}
return 0;
}
盡管名稱如此,但keep-alive並不是要保持連接活動,而是定期交換數據包以確保對等體之間存在網絡路徑。 它會在空閑時殺死延長網絡中斷的連接。
由於這種行為,除非有充分的理由,例如telnet或SSH連接,否則不應使用keep-alive,在客戶端失去聯系時終止會話是合理的。
最有可能的是,由於某些連接處理策略,服務器在n小時后關閉連接,而不管keepalive使用情況如何。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.