syslog-ng: Number of allowed concurrent connections reached, rejecting connection

I have configured syslog-ng as a log server for all of the servers in my network and I noticed that when the number of servers in the network grew, some of them failed to send log messages to the log server. I found this warnings on my log server:

syslog-ng[16834]: Number of allowed concurrent connections reached, rejecting connection; client='AF_INET( X.X.X.X:48236)', local='AF_INET(0.0.0.0:514)', max='10'

By default the number of concurrent connections is 10, to solve the problem I’ve increased the number of concurrent connections in source secction in /etc/syslog-ng/syslog-ng.conf file:

source network {
        udp(ip(0.0.0.0) port(514));
        tcp(ip(0.0.0.0) port(514)  max-connections(50) );
};