tcp 长连接不开启keep alive如果网络中断,客户端看到的还是ESTABLISH状态

客户端 node2 192.168.137.3  


服务端  node1 192.168.137.2



建立连接后断开 node1的网络

node2:/root#netstat -na | grep 8080
tcp        0      0 192.168.137.3:62497         192.168.137.2:8080          ESTABLISHED 
unix  3      [ ]         STREAM     CONNECTED     88080  
You have new mail in /var/spool/mail/root
node2:/root#netstat -na | grep 8080
tcp        0      0 192.168.137.3:62497         192.168.137.2:8080          ESTABLISHED 
unix  3      [ ]         STREAM     CONNECTED     88080  
node2:/root#netstat -na | grep 8080
tcp        0      0 192.168.137.3:62497         192.168.137.2:8080          ESTABLISHED 
unix  3      [ ]         STREAM     CONNECTED     88080  
node2:/root#ping 192.168.137.2
PING 192.168.137.2 (192.168.137.2) 56(84) bytes of data.

在node2上看到,连接还在 但是网络已经ping不通了



tcpdump抓包也没任何动静

node2:/root/test#set -o vi
node2:/root/test#tcpdump -S -i eth1 '((tcp) and  (host 192.168.137.2) and (port 8080) )'
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes


08:52:12.808738 IP node2.62497 > node1.webcache: Flags [S], seq 1669421213, win 14600, options [mss 1460,sackOK,TS val 128247746 ecr 0,nop,wscale 7], length 0
08:52:12.808872 IP node1.webcache > node2.62497: Flags [S.], seq 4191267856, ack 1669421214, win 14480, options [mss 1460,sackOK,TS val 1087430 ecr 128247746,nop,wscale 6], length 0
08:52:12.808910 IP node2.62497 > node1.webcache: Flags [.], ack 4191267857, win 115, options [nop,nop,TS val 128247747 ecr 1087430], length 0
08:52:12.808989 IP node2.62497 > node1.webcache: Flags [.], seq 1669421214:1669422662, ack 4191267857, win 115, options [nop,nop,TS val 128247747 ecr 1087430], length 1448
08:52:12.809066 IP node2.62497 > node1.webcache: Flags [P.], seq 1669422662:1669422674, ack 4191267857, win 115, options [nop,nop,TS val 128247747 ecr 1087430], length 12
08:52:12.809230 IP node1.webcache > node2.62497: Flags [.], ack 1669422662, win 272, options [nop,nop,TS val 1087430 ecr 128247747], length 0
08:52:12.809239 IP node1.webcache > node2.62497: Flags [.], ack 1669422674, win 272, options [nop,nop,TS val 1087430 ecr 128247747], length 0


过了几个小时以后再来查看，依旧是 ESTABLISHED 状态，且 tcpdump 输出显示没有任何包传输。