HostData.guid

public string guid ;

Description

The GUID of the host, needed when connecting with NAT punchthrough.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Start() {
        HostData[] hostData = MasterServer.PollHostList();
        foreach (HostData element in hostData) {
            Debug.Log(element.gameName + " guid: " + element.guid + "\n");
        }
    }
}