Chapter 226: Probes and Boundaries

The elevator descended. The metal car gave him a faint sense of weightlessness. Lin Chen leaned against the handrail, the numbness in his left leg like a thick wad of soaked cotton, heavy around every nerve. He closed his eyes and ran through the probe’s call chain in his head. Callback request. Unauthorized. Firewall interception. Put together, those three phrases meant only one thing in medical informatization: outbound data transmission or unauthorized access. The information department at the Provincial Hospital was not decoration; Level 3 classified protection was a hard line. Any callback from a non-whitelisted IP would trigger an alarm in the zero-trust architecture. He could not gamble on luck. He had to find the source.

Back at the temporary apartment, he did not turn on the ceiling light. He only switched on the desk lamp. The laptop booted. He connected to the internal debugging terminal. The USB drive went in, and he mounted the probe logs. Blue light from the screen fell across his face; dust drifted slowly through the beam. He typed a command and filtered for POST requests and callback fields. The logs began to scroll. The timestamp stopped at 11:42 last night. Target IP: 10.0.88.14. An internal address. But the port was 8443, and the protocol header carried an X-Telemetry field.

He frowned. This was not business data being sent back. It was the health-check probe bundled with an open-source DICOM parsing library. In its default configuration, after the service started, it sent heartbeat packets to a preset telemetry server to count invocation frequency and version distribution. The test set Su Man had given him contained an old dependency package. Last night he had focused only on memory pressure and cache tuning, and had not audited the full dependency tree. One oversight had crossed the hospital’s compliance red line.

Lin Chen did not panic. He opened his mistake notebook, the pen tip cutting across the paper:

“Item 226 continued: Default configuration is a land mine. Open source does not mean exempt from responsibility. Next step: strip out the telemetry module, rewrite the heartbeat logic, and localize log persistence. Submit the explanation document and patch before nine.”

He switched back to the code editor and found dicom_parser/telemetry.py. He commented out the default requests.post call, replaced it with local file writes, and added a configuration switch that was off by default. The change was small, but the dynamic library had to be recompiled. He brought up the cross-compilation environment and set the target architecture to linux-x86_64. The progress bar began to move. In the quiet room, the fan noise sounded harsh, like a low-frequency panting.

His left foot began to cramp. The muscle tightened as if twisted by thin iron wire, jerking beyond his control. He stopped typing and bent down for the safflower oil on the floor. The cap came off, and the sharp smell spread. He poured some into his palm, rubbed it warm, and pressed hard into his calf. Under his fingertips the tendons were rigid as stone. He gritted his teeth. Once, twice. The pain went from dull to sharp, then slowly dispersed. He exhaled, put the bottle back on the corner of the desk, and kept his eyes on the screen. Compilation complete. He packaged the patch and generated the SHA256 checksum.

His phone vibrated. Su Man sent a voice message. Behind her voice were keyboard sounds and the faint workings of a coffee machine. “Lin Chen, I’ve already spoken to the information department. They’re not targeting you; it’s compliance procedure. But tomorrow’s nine o’clock demo will have the hospital director and the neurosurgery chief present. The data has to be clean, and the system can’t crash. Can the patch go in?”

Lin Chen typed back: “Yes. The telemetry module has been stripped out. Heartbeats now write to local storage. I’ll send you the test package within ten minutes. Also, the demo environment needs external network access disabled and must go through a pure intranet proxy. I’ll configure the routing table in advance.”

Su Man replied instantly: “Good. The advance payment will arrive before three this afternoon. Take care of your body first. Don’t force yourself too hard.”

Lin Chen did not reply with “okay.” He closed the chat window and dragged the patch package and a three-page Technical Explanation of Probe Callback Requests into an email attachment. Recipient: the Provincial Hospital Information Department Security Group. CC: Su Man. The body contained only one sentence: “The default telemetry configuration has been located and repaired. Patch and checksum are attached. The system has been adjusted to pure intranet mode and meets Level 3 classified protection requirements. Hot update can be completed before tomorrow’s demonstration.”

He clicked send. The time read 3:20 a.m.

He leaned back in the chair and rubbed the center of his brow. Outside the window, the sky was still dark, with only the streetlights on the distant overpass connected into a dim yellow line. He stood. When his left foot touched the floor it was still weak, but it could bear weight. He picked up his coat and went out.

The hospital corridor was much quieter than during the day. Only the call bell at the nurses’ station rang once in a while. The smell of disinfectant mixed with the damp odor of old wall paint and pressed heavily into the air. He pushed open the ward door. Xiaoman lay on his side, breathing lightly. The picture book on the bedside table had been turned to a new page. It showed a bulky machine, and beside it, in crooked writing: “Brother’s star.” Lin Chen sat down on the folding chair by the bed. He did not turn on the light. He watched the rise and fall of his brother’s shoulders, his fingers unconsciously rubbing the hard cover of the mistake notebook.

Twenty thousand yuan for the deposit had gone through. The transfer form had been signed. The agreement would be signed tomorrow. The demonstration would run tomorrow. Every step felt like walking on thin ice. But he knew that beneath the ice was not an abyss. It was a road. As long as he did not step wrong, he could cross it. He did not need comfort. He only needed results.

He took out his phone and sent Old Zhao a text message. It was not a demand for payment, but a progress update. “Brother Zhao, the underlying layer of the medical imaging parser has been adapted to the Provincial Hospital’s private protocol. Performance stress testing has passed. If other top-tier hospitals need integration later, this architecture can be reused. The quotation has been updated and sent to your email.”

Old Zhao did not reply. That was normal. Old Zhao was a businessman; he only looked at results. Lin Chen did not wait. He put the phone away, took the thermos from his bag, and drank a mouthful of strong tea that had already gone cold. The bitter taste slid down his throat and suppressed the emptiness in his stomach.

He opened the mistake notebook and wrote on a new page:

“Item 227: Technology is a tool; compliance is the threshold. Clinical departments do not care how pretty the code is, only whether the result is stable. Tomorrow at nine is not a demonstration. It is acceptance. Next step: arrive at the server room one hour early and verify the network topology. Bring two printed operation manuals. Confirm backup power.”

He closed the notebook and leaned back in the chair. From the end of the corridor came the sound of cart wheels rolling over floor tiles, approaching from far away, then gradually receding. The morning-shift nurses had begun their rounds.

The phone screen suddenly lit up. It was not a text message, but an automatic push notification from the hospital’s internal system:

“[Information Department] Special channel privileges have been temporarily restored. Please complete system access verification before 08:30 tomorrow. Note: This demonstration will simultaneously connect to the Provincial Health Commission’s data supervision platform. All operation logs must be reported in real time. The audit interface has been opened.”

Lin Chen stared at the line of text. Supervision platform. Real-time reporting. Audit interface.

He slowly sat up straight. His left foot was numb, but his back was very straight. He knew the firewall was only the first door. Behind that door was another, stricter set of rules. And rules never cared about human circumstances. They only recognized results. The margin for error had been compressed to zero. Tomorrow, the system could not merely run through. It had to run steadily. Any memory overflow or network jitter would be exposed directly in the regulatory logs.

He picked up his pen and added one more line to the mistake notebook:

“Regulatory connection. Log audit. Zero tolerance. Tomorrow, it cannot just run; it has to run steadily. Enter the site two hours early. Bring the offline rollback package.”

Outside the window, the sky began to pale. The first thread of morning light climbed onto the windowsill and landed on the pages of the mistake notebook. The ink had not yet dried. He stood, packed the computer into his backpack, and the sound of the zipper closing was very soft in the empty corridor. He pushed open the door and walked toward the elevator. His left foot still hurt when it landed, but his steps did not falter. For the next six hours, there would be no buffer—only execution.