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UDP communication port be occupied caused SoftCo attendant position one-way audio

Publication Date:  2012-10-08 Views:  406 Downloads:  0

Issue Description

The two PC connected with SoftCo9500 separately equipped with attendant position software SoftCo Console System. SoftCo version is V100R002C03, two PC IP addresses are and respectively, the whole networking as below:
PC1( - switch - PC2(
 In the process customers use the attendant position, found the attendant position one-way audio fault, the phenomenon was after the conversation has been establishment, from PC2 can hear the voice of PC1, but from PC1 can’t hear the voice of PC2.

Alarm Information


Handling Process

1, first communicate with customer, ruled out four kinds of peripherals and configuration may cause the possibility of one-way audio and then asked to customers do analysis on the PC can’t hear the peer end.
2, after analytical through the WireShark capture tools, observe one-way audio communication’s voice oscillograph, and receive the conversation speech, decision can't hear the IP of the PC which can’t hear the peer end voice is
3, through the WireShark analytic the SIP call process to observe SIP protocol communication process, found PC2 send response message “200 OK” at 35.645 ms. From SIP call process can see, call is launched by PC1, after the PC2 return the “200 OK” message and establish session with PC1, an equipment whose IP is sending RTP message to PC2’s 9000 port, and the RTP message sent from PC1 to PC2 will also be sent to the PC2’s 9000 port.
4, analysis suspicious message.
Because of RTP message uses UDP protocol in the transport layer, and now that there is a equipment whose IP is is sending RTP message to PC2’s 9000 port, so observe the filtering message, in 35.66 seconds this time begin to discover a suspicious message (chose 35.66 seconds this time observation, because PC2 sent "200 OK" message to PC1 is 35.645 seconds), began from 35.66 seconds, the equipment has been sent RTP message to PC2’s 9000 port.
5, after analysis, it is a certain equipment whose IP is constant through the UDP protocol sending RTP message to PC2’s 9000 port, and then occupies PC2’s UDP communication port, so the RTP message sent from PC1 to PC2 in call process cannot be received by PC2.
6, after confirm with the customer, there is a UA5000 equipment whose IP is, after the customer disconnected the network between UA5000 and PC2, the one-way audio problem solving.

Root Cause

 1, the headphone is not in use.
2, computer sound card set wrong.
3, attendant position client or PC is set mute voice.
4, microphone sound is too small.
5, network reasons, need analysis through capture packages


When SoftCo attendant position one-way audio occurs, first of all find out reason from the PC peripherals and software configuration, if everything is all right, need to capture network message in a one-way audio PC, and analysis SIP communication process, RTP stream and UDP protocol port occupy situation.