Review the "txpi" file in your $XCOM_HOME/txpi directory on your Unix/Linux system. You will see 4 different "txpi" files, one for each protocol you use. If you are just performing a simple IPV4 transfer then you will need to edit the "txpi" file.
txpi file corresponds to XCOM IPv4 txpis file corresponds to XCOM IPv4 SSL txpi6 file corresponds to XCOM IPv6 txpi6s file corresponds to XCOM IPv6 SSL
In that file and all other files you will see 2 lines that are commented as shown below:
# per_source = 10 # instances = 50
You would need to uncomment the above lines in the file and configure the values per your requirements.
Please keep in mind that you may need to stop/start xcomd and possibly your xinetd service.