TCP IP network initial IP problem/ how do users know initial IP ?

Hi, I kindly need your help. I have a STM32F769 and TCP server application . I am using LWIP stack . In my application server is arm and PC is client. When client tries to send something to arm, arm binds client’s ip address. So the connection is ok for reception and transmission. Client can change Ip address (if client wants) or another Network parameters also. But what if client forgot arm’s ip address ? I tried cmd arp -a command to list mac and ip address (bcs I know mac address) but it did not work. But when I ping to arm or send another data form pc to arm then arp -a gives me correct ip and mac address for arm. So is there any code or application or gui that we use to get ip address ? I am not sure that tcp server application is appropriate for this. Also Our client (pc) is not only one . It can be changed.(users need to use another PC ) So maybe we need a connection between client and server even their ip address cannot be known. I am not good at network protocols and network applications . So your help would be much appreciated. Thanks.

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