This library can help you to get a list of running processes, get a list of tcp ports opened by the process, and find a process by the tcp port it opened.

Just pass the pid of process to the function getLocalTcpPorts(of: pid_t).

let result = getLocalTcpPorts(of: 56605)
print(result)

It's quite easy to get all the TCP ports opened by one process with a command.

lsof -nP -p <pid> -a -i4TCP

However, if you need to do the job programmatically with Swift in macOS. There's no available documented API to do this.
So I use below functions from libproc just like the command lsof do.

• proc_pidfdinfo
• proc_pidinfo

Just use getAllProcess().

for process in getAllProcess() {
    print(process.pid, process.name)
}

let process = getProcess(from: 13659)