The contract between EPG Client and EPG Web allows TCP communication initiated by the client toward the webserver with TCP destination port 80. This means that the host in EPG Client can establish a connection to the webserver in EPG Web on TCP port 80. However, the contract does not allow the webserver to initiate a connection back to the host on the same port, which is typically used for HTTP traffic.
References: The explanation is based on the understanding of Cisco Application Centric Infrastructure (ACI) contracts, which are used to define the communication between EPGs (Endpoint Groups). For more detailed information, refer to the Cisco Data Center Core Technologies source book and the ACI documentation available on Cisco's official website.