Hello Aaron
Great to have you with us Aaron!
The load balancing algorithms that are available for etherchannel depend on the platform being used. Most lower end platforms will only use source and destination MAC and IP addresses. Higher end devices such as the 4500/9400/6500/6800/9600 series devices allow you to use algorithms that also take into account the source and destination Layer 4 ports. The following is an example of a Cisco command reference that further describes this.
So in your scenario, of one host and one server, and if you are using FTP for example, you could theoretically create multiple FTP file transfers, each of which will have a different source port (from the point of view of the client) and a single destination port (from the point of view of the FTP server). If your load balancing algorithm is configured to use source ports (for the client → server direction) or destination ports (for the server → client direction) , then each file transfer may use a different physical link.
The load balancing feature needs to have each individual session go over a single link. A session is a communication between two hosts with the same source and destination MAC, IP, and Port numbers. There is no way that etherchannel can separate a session over two or more links. This is done in order to avoid out of order delivery.
I hope this has been helpful!
Laz