Puzzles about the failure of the net send command

Note: There are two workstations in the LAN. When messages are sent to each other using the "net send" command embedded in the Windows system, two fault prompts are displayed, so why are there different fault prompts for the same "net send" command? How can we solve this problem to solve the problem that the net send fails to succeed?

There are two workstations in the LAN. When messages are sent to each other using the "net send" command embedded in the Windows system, two fault prompts are displayed, so why are there different fault prompts for the same "net send" command? How can we solve this problem to solve the problem that the net send fails to succeed? Now I will contribute specific fault phenomena and troubleshooting processes for your reference!

　　Fault symptom

There are two workstations in the LAN: A and B. in the LAN, the workstation a is installed with Windows XP, the IP address is 192.168.1.10, And the workstation B is installed with Windows 2003, it uses the IP address 192.168.1.20. When the author tries to execute the string command "net send 192.168.1.20 test" in workstation a to send a Test message to workstation B, the workstation a system prompts a "general network error occurred" fault and prompts "Enter net helpmsg 2136 for more help; when the author tries to execute the string command "net send 192.168.1.10 test" in the system of workstation B to send a Test message to the system of workstation, workstation B's system prompts "the alias for this message cannot be found on the network, the prompt message "Enter net helpmsg 2273 for more help" is also displayed. Why are different fault prompts and different information help numbers displayed when the same "net send" command is executed on two different workstations in the lan, how can we solve this problem to solve the problem that the net send fails to succeed?

　　Troubleshooting

According to the prompt "Enter net helpmsg 2136 for more help" popped up in the system of workstation A, the author immediately executed the "net helpmsg 2136" string command in the system of workstation, on the result page shown in the following figure, I learned that the cause of the fault is probably that the network hardware is damaged. Isn't it a problem with hardware devices such as the network connection line or network adapter? To verify this analysis, I run the "Ping 192.168.1.20" string command in the system to ping the workstation. The result shows that the command is successfully executed, this indicates that there is no problem with the physical line and nic equipment between workstation A and workstation B. After the possibility of network hardware damage is ruled out, what causes the system to prompt "general network errors? Will the "net send" command used by workstation a fail itself? To check whether the "net send" command runs normally in the system of workstation A, the author runs the "net send 192.168.1.10 test" string command in the system, try sending a message to yourself. The final result is "The message has been successfully sent to 192.168.1.10 ", this indicates that the "net send" string command runs normally in the workstation system. Through the above investigation and analysis, the author estimates that it is likely that the system of workstation B has encountered problems.

Figure 1

According to the prompt "Enter net helpmsg 2273 for more help" popped up by workstation B, the author also executed the "net helpmsg 2273" string command in workstation B, in the result page shown in figure 2, I found that the fault may be caused by the failure of workstation B to correctly interpret the "net send" command. To check whether the "net send" command runs normally in the system of workstation B, the author runs the "net send 192.168.1.20 test" string command in the system, try to send a Test message to yourself. The final result is also "the alias for this message cannot be found on the network ", is it true that the "net send" command in this system is damaged? The author reluctantly continued to execute the "net send 192.168.1.30 test" string command and tried to send a Test message to another workstation, the final result is "The message has been successfully sent to 192.168.1.30", which indicates that the "net send" string command runs normally in the system of workstation B.

Figure 2

 

In workstation B, why can I use the "net send" command to send messages to others, but cannot send messages to myself or workstation? I have been thinking for a long time, and I have never come up with a solution. I had to go online and search for the specific usage information of the "net send" command. I found out by searching for information, to receive a message from someone else, you must log on to the Windows Workstation system correctly and run the "messenger" system service in the system correctly. Comparing the two conditions, the author estimates that the reason why the system of workstation B cannot send messages to itself is probably that the system service of the system "messenger" is accidentally stopped; based on my estimation, I right-click my computer on the desktop of workstation B and execute the "manage" command from the shortcut menu that appears, open the Computer Management window of the corresponding workstation system. In the left-side pane of the window, expand "Computer Management", "services and applications", and "services" branch projects, in the subpane on the right of the corresponding "service" project, double-click "messenger" system service with the mouse to open the service attribute setting interface shown in 3, on this page, I found that the "messenger" System Service of workstation B is disabled, it seems that workstation B cannot send messages to itself. The "sin" is the "messenger" service. After finding the cause of the failure, I quickly click the "Start" button in Figure 3 to restart the service and set the Service Startup type to "automatic ", make sure that the service is not stopped after the system is restarted. After the "messenger" system service is started, the author tries to execute the "net send 192.168.1.20 test" string command in the system of workstation B, the error message "the alias for this message cannot be found on the network" is not displayed again, so far, the "alias for this message cannot be found on the network" Fault on workstation B has been successfully solved!

 

Figure 3

I thought that when I sent a message from workstation B to workstation A, there would be no "alias for this message not found on the network" fault, but after the practical test, it is found that this fault still exists when "messenger" system service is enabled on workstation B. Through the above troubleshooting and analysis, I have basically confirmed that the "net send" command runs normally in the system of workstation A and workstation B, and the message reception function of each workstation is also normal; what puzzles the author is: why can't the two workstations send messages successfully? Is there a problem with the physical line between two workstations A and B? I am not at ease, and in the MS-DOS window of the B workstation system executed a "Ping 192.168.1.10" string command, want to verify whether the ping from the B workstation a workstation, however, I was surprised by the results of this execution. There was a prompt such as "request timed out". No wonder workstation B could not send messages to workstation. Considering that workstation a can ping workstation B, and workstation B can send messages to other workstations, the author estimates that the physical line between workstations A and B is certainly no problem, in addition, the system settings of workstation B should not be faulty. The problem is probably that the system settings of workstation a are incorrect, this error may be the root cause of different fault prompts when two workstations use the "net send" command to send messages to each other.

Based on the above analysis, the author returned to the workstation system and carefully checked the network parameters of the system. I first opened the "local connection" attribute setting window of workstation A, and selected the "Internet Protocol (TCP/IP)" option in the window, and then click the "properties" button, enter the TCP/IP parameter settings window. In this window, I checked the IP address and gateway parameters, and found that everything is normal. In the close TCP/IP parameter settings window, when I returned to the "local connection" attribute setting window, I suddenly looked at the "advanced" tab of the window and thought that the Windows XP system SP2 patch package was just installed a few days ago, it is said that the patch package has enhanced and improved the firewall functions. is the failure of the firewalls of the system caused by the inability of workstations A and B to send messages to each other?

Here, I quickly clicked the "advanced" tab in the "local connection" attribute setting window, and then clicked the "Settings" button on the corresponding tab to open the firewall parameter setting interface; when the "exceptions" tab page is displayed, the "file and printer sharing" item is not selected (4 ), will this project be the final "sin? Take a try and select the "file and printer sharing" project and click "OK; and then executed a "Ping 192.168.1.10" string command in the MS-DOS window of workstation B, this time found that workstation a can ping, when I run the "net send 192.168.1.10 test" string command again, I found that workstation B can now successfully send messages to workstation a through the "net send" command, in addition, when the "net send 192.168.1.20 test" string command is executed from the system of workstation A, the execution result is also successful, this indicates that the fault that two workstations A and B cannot send messages to each other is caused by improper firewall parameter settings of workstation. At this point, the two workstations cannot use the "net send" command to send messages to each other!

Figure 4

　　Fault Summary

At this point, this article can come to an end. However, what I don't understand is why all faults disappear when I select the "file and printer sharing" project on the "exceptions" tab of the firewall. After checking the information on the Internet, I finally figured out the reason. The original "file and printer sharing" service was associated with the four service ports of the system, they are "UDP 137", "UDP 138", "tcp 139", and "TCP 445" respectively, once the "file and printer sharing" service is not selected in the firewall, the "tcp 139" and "TCP 445" ports in workstation A will be disabled, the ping command uses the TCP 445 port for communication, and the net send command uses the tcp 139 port for communication, in this case, when we run the "Ping 192.168.1.10" string command in the system of workstation B, a prompt such as "request timed out" will naturally pop up, when you try to send a message to workstation A, the error message "the alias for this message cannot be found on the network" appears. When the "messenger" System Service in workstation B is disabled, when we send a message from workstation a to workstation B, the error message "common network errors" appears.

To sum up the troubleshooting process above, I believe that in the process of troubleshooting network faults, we should focus on the network parameters and network hardware that are directly linked with the occurrence of faults, we also need to consider the Interference Factors of the built-in firewall. When troubleshooting specific faults, we must analyze them one by one, think carefully, and eliminate them one by one to quickly and effectively solve the fault.