diff --git a/doc/changelog.d/3540.fixed.md b/doc/changelog.d/3540.fixed.md
new file mode 100644
index 0000000000..b524a5f16d
--- /dev/null
+++ b/doc/changelog.d/3540.fixed.md
@@ -0,0 +1 @@
+fix: checking port on non-grpc mapdl instances
\ No newline at end of file
diff --git a/src/ansys/mapdl/core/cli/list_instances.py b/src/ansys/mapdl/core/cli/list_instances.py
index 644fa75d00..36d6d5b9df 100644
--- a/src/ansys/mapdl/core/cli/list_instances.py
+++ b/src/ansys/mapdl/core/cli/list_instances.py
@@ -125,9 +125,13 @@ def get_port(proc):
         ind_grpc = cmdline.index("-port")
         return cmdline[ind_grpc + 1]
 
+    def is_grpc_based(proc):
+        cmdline = proc.cmdline()
+        return "-grpc" in cmdline
+
     table = []
     for each_p in mapdl_instances:
-        if instances and not each_p.ansys_instance:
+        if not each_p.ansys_instance or not is_grpc_based(each_p):
             continue
 
         proc_line = []