The near-end and far-end ports may have identical pinouts, so using a straight-through cable will result in one TX pin being connected to another TX pin.
But before you replace the cable, double-check your pinouts. If the cable fails the loopback test, you might need to replace the cable. Make a Telnet or proxy connection to the near-end device and perform a loopback test. Unplug the cable at the far end and loop the TX pin to the RX pin. The next step is to test the problem port's cable. If the result of the loopback test is different, the port may be defective. If the result of the loopback test is exactly as described in Step 3, the port is physically OK. Without the loopback, you should not see the character echoed. Now remove the paper clip from the port and type a character. You should see the character echoed on the screen. Perform a loopback test: Type any character. If the device will support it, make a Telnet or proxy connection to the near-end device. Take a paper clip or screwdriver and loop the port's TX pin (typically Pin 2 on RS-232 ports) to its RX pin (typically Pin 3 on RS-232 ports). Remove the cable from the near-end port of the problem connection. With that established, you can move on to testing cables, protocols, and other equipment in your system. Shorting pins can confirm that your device and its data port are working properly. In our work with remote monitoring and control systems, DPS Tech Support reps frequently help our clients use loopback testing to troubleshoot RTUs that aren't reporting alarms correctly. When you're setting up any kind of communication serial device, you'll probably have to troubleshoot data ports activity at some point. Loopback is a good RS-232 check tester method. 
Use a screwdriver to loop pins for testing.
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