.Em net.inet.ip.portrange.first

and

.Em net.inet.ip.portrange.last

tunables default to 1024 and 5000, respectively. These, like many other

sysctl tunables, are designed to limit the use of kernel resources

(i.e. port number space) unless there is an explicit requirement for

more than this reasonable default.  These are the port numbers

allocated to sockets which were created with a 

.Xr socket 2

call where

the port number parameter was zero.  This default range of ports (3977

in total) is likely to be insufficient for a machine running a number

of client programs of whatever description. The 'first' tunable can't

be set below 1024, but may be set higher.

The 'last' tunable will usually be the one that requires tweaking on

a machine with numerous clients (that don't make use of the IP_PORTRANGE

.Xr setsockopt 2

option). Assuming you have enough file descriptors and your client

code uses

.Xr perror 3 ,

you will see a message like "Can't assign requested address"

(EADDRNOTAVAIL) or "Resource temporarily unavailable" (EAGAIN) if this is set

too low for your application. See /usr/src/sys/netinet/in.h for more

discussion.

.Pp

The