diff --git a/test/functional/p2p_invalid_messages.py b/test/functional/p2p_invalid_messages.py
index dbf9c057a5..3fdec2a488 100755
--- a/test/functional/p2p_invalid_messages.py
+++ b/test/functional/p2p_invalid_messages.py
@@ -15,7 +15,7 @@ class msg_unrecognized:
 
     command = b'badmsg'
 
-    def __init__(self, str_data):
+    def __init__(self, *, str_data):
         self.str_data = str_data.encode() if not isinstance(str_data, bytes) else str_data
 
     def serialize(self):
@@ -25,19 +25,14 @@ class msg_unrecognized:
         return "{}(data={})".format(self.command, self.str_data)
 
 
-class msg_nametoolong(msg_unrecognized):
-
-    command = b'thisnameiswayyyyyyyyytoolong'
-
-
 class InvalidMessagesTest(BitcoinTestFramework):
-
     def set_test_params(self):
         self.num_nodes = 1
         self.setup_clean_chain = True
 
     def run_test(self):
         """
+         . Test msg header
         0. Send a bunch of large (3MB) messages of an unrecognized type. Check to see
            that it isn't an effective DoS against the node.
 
@@ -45,10 +40,12 @@ class InvalidMessagesTest(BitcoinTestFramework):
 
         2. Send a few messages with an incorrect data size in the header, ensure the
            messages are ignored.
-
-        3. Send an unrecognized message with a command name longer than 12 characters.
-
         """
+        self.test_magic_bytes()
+        self.test_checksum()
+        self.test_size()
+        self.test_command()
+
         node = self.nodes[0]
         self.node = node
         node.add_p2p_connection(P2PDataStore())
@@ -63,7 +60,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
         # Send as large a message as is valid, ensure we aren't disconnected but
         # also can't exhaust resources.
         #
-        msg_at_size = msg_unrecognized("b" * valid_data_limit)
+        msg_at_size = msg_unrecognized(str_data="b" * valid_data_limit)
         assert len(msg_at_size.serialize()) == msg_limit
 
         with node.assert_memory_usage_stable(increase_allowed=0.5):
@@ -90,10 +87,10 @@ class InvalidMessagesTest(BitcoinTestFramework):
         #
         # Send an oversized message, ensure we're disconnected.
         #
-        msg_over_size = msg_unrecognized("b" * (valid_data_limit + 1))
+        msg_over_size = msg_unrecognized(str_data="b" * (valid_data_limit + 1))
         assert len(msg_over_size.serialize()) == (msg_limit + 1)
 
-        with node.assert_debug_log(["Oversized message from peer=0, disconnecting"]):
+        with node.assert_debug_log(["Oversized message from peer=4, disconnecting"]):
             # An unknown message type (or *any* message type) over
             # MAX_PROTOCOL_MESSAGE_LENGTH should result in a disconnect.
             node.p2p.send_message(msg_over_size)
@@ -109,7 +106,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
         # Send messages with an incorrect data size in the header.
         #
         actual_size = 100
-        msg = msg_unrecognized("b" * actual_size)
+        msg = msg_unrecognized(str_data="b" * actual_size)
 
         # TODO: handle larger-than cases. I haven't been able to pin down what behavior to expect.
         for wrong_size in (2, 77, 78, 79):
@@ -136,18 +133,58 @@ class InvalidMessagesTest(BitcoinTestFramework):
             node.disconnect_p2ps()
             node.add_p2p_connection(P2PDataStore())
 
-        #
-        # 3.
-        #
-        # Send a message with a too-long command name.
-        #
-        node.p2p.send_message(msg_nametoolong("foobar"))
-        node.p2p.wait_for_disconnect(timeout=4)
-
         # Node is still up.
         conn = node.add_p2p_connection(P2PDataStore())
         conn.sync_with_ping()
 
+    def test_magic_bytes(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        conn.magic_bytes = b'\x00\x11\x22\x32'
+        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: INVALID MESSAGESTART ping']):
+            conn.send_message(messages.msg_ping(nonce=0xff))
+            conn.wait_for_disconnect(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
+    def test_checksum(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['ProcessMessages(badmsg, 2 bytes): CHECKSUM ERROR expected 78df0a04 was ffffffff']):
+            msg = conn.build_message(msg_unrecognized(str_data="d"))
+            cut_len = (
+                4 +  # magic
+                12 +  # command
+                4  #len
+            )
+            # modify checksum
+            msg = msg[:cut_len] + b'\xff' * 4 + msg[cut_len + 4:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.sync_with_ping(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
+    def test_size(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['']):
+            msg = conn.build_message(msg_unrecognized(str_data="d"))
+            cut_len = (
+                4 +  # magic
+                12  # command
+            )
+            # modify len to MAX_SIZE + 1
+            msg = msg[:cut_len] + struct.pack("<I", 0x02000000 + 1) + msg[cut_len + 4:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.wait_for_disconnect(timeout=1)
+            self.nodes[0].disconnect_p2ps()
+
+    def test_command(self):
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['PROCESSMESSAGE: ERRORS IN HEADER']):
+            msg = msg_unrecognized(str_data="d")
+            msg.command = b'\xff' * 12
+            msg = conn.build_message(msg)
+            # Modify command
+            msg = msg[:7] + b'\x00' + msg[7 + 1:]
+            self.nodes[0].p2p.send_raw_message(msg)
+            conn.sync_with_ping(timeout=1)
+            self.nodes[0].disconnect_p2ps()
 
     def _tweak_msg_data_size(self, message, wrong_size):
         """
diff --git a/test/functional/test_framework/mininode.py b/test/functional/test_framework/mininode.py
index 1a7ef0aec5..f61fd212e9 100755
--- a/test/functional/test_framework/mininode.py
+++ b/test/functional/test_framework/mininode.py
@@ -152,10 +152,10 @@ class P2PConnection(asyncio.Protocol):
         # The initial message to send after the connection was made:
         self.on_connection_send_msg = None
         self.recvbuf = b""
-        self.network = net
+        self.magic_bytes = MAGIC_BYTES[net]
         self.uacomment = uacomment
 
-        if self.network == "devnet":
+        if net == "devnet":
             devnet_name = "devnet1"  # see initialize_datadir()
             if self.uacomment is None:
                 self.strSubVer = MY_SUBVERSION % ("(devnet.devnet-%s)" % devnet_name).encode()
@@ -217,7 +217,7 @@ class P2PConnection(asyncio.Protocol):
             while True:
                 if len(self.recvbuf) < 4:
                     return
-                if self.recvbuf[:4] != MAGIC_BYTES[self.network]:
+                if self.recvbuf[:4] != self.magic_bytes:
                     raise ValueError("magic bytes mismatch: {} != {}".format(repr(self.magic_bytes), repr(self.recvbuf)))
                 if len(self.recvbuf) < 4 + 12 + 4 + 4:
                     return
@@ -279,7 +279,7 @@ class P2PConnection(asyncio.Protocol):
         """Build a serialized P2P message"""
         command = message.command
         data = message.serialize()
-        tmsg = MAGIC_BYTES[self.network]
+        tmsg = self.magic_bytes
         tmsg += command
         tmsg += b"\x00" * (12 - len(command))
         tmsg += struct.pack("<I", len(data))