While performing a connection with Salesforce through a proxy you have to put proxy parameters either inside TIBCOBusinessStudio.ini and/or inside VM arguments. 

Example:

-Dcom.tibco.plugin.salesforce.proxyHost=10.97.102.228 
-Dcom.tibco.plugin.salesforce.proxyPort=8099
-Dcom.tibco.plugin.salesforce.proxyTimeout=15000

If you have a space before the port number

-Dcom.tibco.plugin.salesforce.proxyPort= 8099

then if you have kept a space before the port number inside the the VM arguments, you can do a successful connection with Salesforce through a proxy. But if you have put a space before the port number inside the TIBCOBusinessStudio.ini file, then you will get following error.

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java.lang.NumberFormatException: For input string:"(space)<port_number>"....
*****

Error ***java.lang.NumberFormatException: For input string:"(space)"....***

Tibco ActiveMatrix BusinessWorks 6.3.5

You will see a java.lang.NumberFormatException if you put a space before the port number inside TIBCOBusinessStudio.ini file because the property Dcom.tibco.plugin.salesforce.proxyPort accepts a string value and tries to convert it into a number. If the string value does not contain a valid number (as in our case, i.e., a space is not a valid number) then it gives the following error.

*****
java.lang.NumberFormatException: For input string:"(space)<port_number>"....
*****

You will not see this error if you put space in front of port value inside VM arguments because VM arguments ignore the space. The next time, if you will try to edit the VM arguments again then you will not see the space in front of port number value.