[Winpcap-users] Two way traffic collision?

Gianluca Varenni gianluca.varenni at cacetech.com
Thu Jun 25 12:33:39 PDT 2009

Are you using the same pcap_t handle for both reception and transmission?

Have a nice day
  ----- Original Message ----- 
  From: Emma Jin 
  To: winpcap-users at winpcap.org 
  Sent: Thursday, June 25, 2009 10:14 AM
  Subject: [Winpcap-users] Two way traffic collision?


        I ran into problem again and am coming to ask for help again:)

        I have three PCs, let's say A, B, and C. A and C both connect to B directly (B has multiple NICs). 

        I am running an application on B. The application starts one thread for each NIC connecting to A and C. The thread listens for incoming packets and replaces the source and destination MAC address and sends the packets out through the other NIC (so the packets from A will be forwarded to C, and the packets from C will be forwarded to A). 

        I tested the application with video. I sent the video (with bandwidth of 2M) from A to C. No problem. I sent five videos (total bandwidth of about 10M) from A to C. No problem. I tried the other way from C to A. No problem either. But whenever I tried two way traffic (both from A to C and from C to A), even if there is only one video each way, the packets got lost. 

        It seems the two way traffic are affecting each other. Is there anything special I need to do to resolve this problem? I am using pcap_next_ex and pcap_sendpacket to receive and send the packets. All of my PCs are running XP.

        Thank you,



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