Yes, it's possible, the syntax is curl [protocol://]<host>[:port]
, for example:
curl example.com:1234
If you're using Bash, you can also use pseudo-device /dev
files to open a TCP connection, e.g.:
exec 5<>/dev/tcp/127.0.0.1/1234
echo "send some stuff" >&5
cat <&5 # Receive some stuff.
See also: More on Using Bash's Built-in /dev/tcp File (TCP/IP).