Marcel Kirsch wrote:

it is correct that there is a router (with NAT) between the slave server and the internet. I tried the solution of Mike (socket = l:SO_KEEPALIVE=1...), but it didn't work. I googled SO_KEEPALIVE and discovered that it only sends a keep alive packet every 2 hours by default. Unfortunately the connection is closed after a shorter time (about 30 minutes). Do you know how it is possible to set the keep alive time to a shorter value?

On Linux you can use: echo 300 > /proc/sys/net/ipv4/tcp_keepalive_time Best regards, Mike