scripts: west_commands: runners: fix support for JLink RTT

JLink refuses new RTT telnet connections for a few moments after a socket
closes. This causes an issue when using `nc` as the telnet viewer, since
JLink would deny the connection. To resolve this, keep the "ping" socket
we use to determine if the RTT viewer is active connected, and use that
socket for RTT communication.

Signed-off-by: Daniel DeGrasse <[email protected]>

scripts/west_commands/runners/core.py

@@ -920,22 +920,27 @@ def ensure_output(self, output_type: str) -> None:
         # RuntimeError avoids a stack trace saved in run_common.
         raise RuntimeError(err)
 
-    def run_telnet_client(self, host: str, port: int) -> None:
+    def run_telnet_client(self, host: str, port: int, active_sock=None) -> None:
         '''
         Run a telnet client for user interaction.
         '''
-        # If a `nc` command is available, run it, as it will provide the best support for
-        # CONFIG_SHELL_VT100_COMMANDS etc.
-        if shutil.which('nc') is not None:
+        # If the caller passed in an active socket, use that
+        if active_sock is not None:
+            sock = active_sock
+        elif shutil.which('nc') is not None:
+            # If a `nc` command is available, run it, as it will provide the
+            # best support for CONFIG_SHELL_VT100_COMMANDS etc.
             client_cmd = ['nc', host, str(port)]
             # Note: netcat (nc) does not handle sigint, so cannot use run_client()
             self.check_call(client_cmd)
             return
+        else:
+            # Start a new socket connection
+            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            sock.connect((host, port))
 
         # Otherwise, use a pure python implementation. This will work well for logging,
         # but input is line based only.
-        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        sock.connect((host, port))
         sel = selectors.DefaultSelector()
         sel.register(sys.stdin, selectors.EVENT_READ)
         sel.register(sock, selectors.EVENT_READ)

scripts/west_commands/runners/jlink.py

@@ -330,9 +330,7 @@ def do_run(self, command, **kwargs):
                         break
                     except ConnectionRefusedError:
                         time.sleep(0.1)
-                sock.shutdown(socket.SHUT_RDWR)
-                time.sleep(0.1)
-                self.run_telnet_client('localhost', self.rtt_port)
+                self.run_telnet_client('localhost', self.rtt_port, sock)
             except Exception as e:
                 self.logger.error(e)
             finally: