This should be applicable to Grid Control 11.1 as well, but it's been tested in 12.1. If unsure which port to specify in an agent installation, you can always ask the OMS to tell you:

[oracle@oem12oms1 ~]$ emctl status oms -details
Oracle Enterprise Manager Cloud Control 12c Release 12.1.0.1.0
Copyright (c) 1996, 2012 Oracle Corporation.  All rights reserved.
Enter Enterprise Manager Root (SYSMAN) Password :
Console Server Host : oem12oms1.localdomain
HTTP Console Port   : 7789
HTTPS Console Port  : 7801
HTTP Upload Port    : 4890
HTTPS Upload Port   : 4901
OMS is not configured with SLB or virtual hostname
Agent Upload is locked.
OMS Console is locked.
Active CA ID: 1
Console URL: https://oem12oms1.localdomain:7801/em
Upload URL: https://oem12oms1.localdomain:4901/empbs/upload

WLS Domain Information
Domain Name      : GCDomain
Admin Server Host: oem12oms1.localdomain

Managed Server Information
Managed Server Instance Name: EMGC_OMS1
Managed Server Instance Host: oem12oms1.localdomain
[oracle@oem12oms1 ~]$