Connect an FTP client to an HMI panel over Ethernet

What you need

• A laptop with a working wired Ethernet port. Note its current IPv4 address and subnet mask before changing anything, so the office settings go back afterwards.
• An FTP client. FileZilla is the common free desktop client; any client that asks for a host, a port, a user name and a password will do.
• One Ethernet cable, straight or crossover, whichever is on the bench.
• The panel's IP address and the FTP login configured in its project. In this example the panel holds 192.168.1.66; read the real values from the panel's own setup screens.

Check the link LEDs on both ports

1. Connect the cable, laptop to panel, and find the small LED beside each Ethernet port.
2. Reseat the cable at both ends until a LED lights at each port.
3. If one stays dark, try the other cable. Straight and crossover both belong on the bench; the LEDs pick the winner.
4. Keep the run inside Ethernet's 100 m twisted-pair limit, the segment length the standard sets for one cable. A 2 m bench lead sits far inside it.
5. Both LEDs lit, go to addressing. Both still dark after a reseat and a second cable, the fault is power, port or cable. No FTP setting repairs a dark LED.

Set the laptop address to match the panel

1. Open a Command Prompt (Start, then type cmd).
2. Run ipconfig /all. Find the wired adapter cabled to the panel and read its IPv4 address and subnet mask. Ignore the wireless adapter's numbers; they describe a different network. If the panel link will be wireless, that is its own design job, starting with the client: see remote HMI wireless access, client chosen first.
3. Set the wired adapter to a static address in the panel's subnet: 192.168.1.10 with mask 255.255.255.0, against the example panel at 192.168.1.66. The fields sit in the wired adapter's IPv4 properties in the laptop's network settings. Pick a host number between 192.168.1.1 and 192.168.1.254 that nothing else uses; .0 is the network address and .255 is the broadcast, so both stay out of service.
4. Leave the panel at 192.168.1.66. Two devices sharing one address on a link fight each other, and the FTP session drops with them.

Example: does 192.168.1.10 share a subnet with 192.168.1.66?

Inputs. Panel address 192.168.1.66, the address configured in the panel's setup screens. Candidate laptop address 192.168.1.10, the free host number picked in step 3 above. Subnet mask 255.255.255.0 on both devices, the mask set for this small link. The link itself is a 2 m bench cable, one segment well inside the 100 m twisted-pair limit, so cable length plays no part in the result.

Rule. A subnet mask splits an address into a network part and a host part. A mask octet of 255 keeps the matching address octet; a 0 discards it. Two addresses share a subnet when keeping the masked octets leaves the same network number on both.

Arithmetic. Panel: 192.168.1.66 with mask 255.255.255.0 keeps the first three octets, giving network 192.168.1.0. Laptop: 192.168.1.10 with mask 255.255.255.0 keeps the same three octets, giving network 192.168.1.0. 192.168.1.0 equals 192.168.1.0, so both addresses sit in one subnet, and host numbers 66 and 10 differ, so neither address collides.

Result. The laptop at 192.168.1.10 can address the panel at 192.168.1.66 across the direct cable, and a ping returns four replies, each typically under 5 ms on a 2 m bench cable.

Decision. Under mask 255.255.255.0, the first three octets must match exactly and the last octet must differ. Any mismatch among the first three, which is what a wireless adapter's address from another network produces, fails the test, and the panel stays unreachable until the wired adapter carries a 192.168.1.x address.

Ping the panel before opening the FTP client

1. In the same Command Prompt, run ping 192.168.1.66.
2. Four replies, each stamped with a time in milliseconds (under 5 ms is normal on a direct cable), prove the IP path end to end: cable, link, address and mask all pass in one test.
3. Timeouts on a direct cable send you back to the example's check: reread ipconfig /all, confirm the wired adapter holds 192.168.1.10 and 255.255.255.0, and confirm the LEDs still light.
4. On a shared plant network a silent panel can be ping filtering by policy; test from a workstation that normally reaches that switch, or wire the laptop direct for the session.

PLC networks trip on the same detail. One write-up follows a PLC ping failure cleared by correcting the laptop's subnet mask. And when a routine ping test leaves a runtime's ports invisible, PROFINET ports not detected after a ping walks the cleanup.

Connect and read the failure message

1. In the client's quick-connect fields, enter host 192.168.1.66, port 21, and the FTP user name and password configured in the panel's project. Port 21 is FTP's assigned control port; leave it unless the panel's documentation puts the service elsewhere.
2. A directory listing from the panel means the session is open.
3. A failed connect splits into three cases, and the message tells you which:
   • Timeout or unreachable: the IP path is still broken; go back to the ping step.
   • Connection refused: the laptop reached the panel and no service answered on port 21; enable the panel's FTP service in its project or set the port it actually uses.
   • Login rejected with code 530: path and port are good and the credentials are wrong; correct them in the panel's project, because the client must match what the panel stores, case included.
4. Services fail separately. A panel whose web server stops responding while FTP still works is a normal sight; one dead service says nothing about the others.

How to check it worked

1. The client lists the panel's directory without errors.
2. Upload a small test file, about 4 kB of text, into the panel's web page folder.
3. Open the panel's browser page from the laptop and confirm the file or the edited page appears. Reload the page on the panel itself if it holds an old copy.
4. Record the panel address, the temporary laptop settings and the FTP login where the next person will find them.
5. Return the laptop to the address and mask noted before you started, so it rejoins the office network cleanly.

A panel reached through an Ethernet serial server follows its own route; programming a panel through an Ethernet serial server covers that setup. And when the finished page deserves a wider audience on the floor, a separate notice screen can carry it; that is the job we build shop-floor screens for.

Recommendation: for a one-off session with a panel at 192.168.1.66, set the laptop to 192.168.1.10 with mask 255.255.255.0, judge the cable by the LEDs, ping before opening the client, and restore the laptop's office settings afterwards. On a shared switch, keep the panel's address inside the site's own subnet and leave the laptop on DHCP; the three-octet check in the example decides reachability there too.

Questions