We have a web server that serves mobile clients, among them G1 running Android. There's a communication problem at the TCP level.
Using tcpdump I've been able to capture the traffic between Android and the web server (actually haproxy load balancer). Then loading it into Wireshark for analysis. Looks like a client doesn't see a server's ACK, and the server doesn't see a client's ACK. This problem is not just for one client, but happens for many (Wifi connection or not). We have other mobile phones connecting, such as the iPhone, and the problem doesn't happen there. Any ideas what's going on here? Example #1 -- client submits an HTTP GET request. server ACK's it, and sends an HTTP reply with status 200. client doesn't see the ACK, and resubmits the request, which the server ACKs again. client never ACKs the server, instead resubmits its request. since client never ACKs, the server resubmits, which the client never ACKs either. "client" -- substituted for the client's IP address "server" -- substituted for the server's IP address TCP packet capture: No. Time Source Desti Proto Info 13991 137.948540 client server TCP 28272 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 WS=2 13992 137.948560 server client TCP http > 28272 [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1460 WS=7 13993 137.965352 client server TCP 28272 > http [ACK] Seq=1 Ack=1 Win=5840 Len=0 13994 137.965604 client server HTTP GET /... HTTP/1.0 Seq=1 Len=408 13995 137.965612 server client TCP http > 28272 [ACK] Seq=1 Ack=409 Win=6912 Len=0 14008 137.973216 server client HTTP HTTP/1.1 200 OK (text/ html) 14617 140.965638 client server HTTP [TCP Retransmission] GET /... HTTP/1.0 Seq=1 Len=408 14618 140.965647 server client TCP [TCP Dup ACK 14008#1] http > 28272 [ACK] Seq=2921 Ack=409 Win=6912 Len=0 SLE=1 SRE=409 14619 140.969611 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK (text/html) 15317 146.964751 client server HTTP [TCP Retransmission] GET /... HTTP/1.0 15318 146.964764 server client TCP [TCP Dup ACK 14619#1] http > 28272 [ACK] Seq=2921 Ack=409 Win=6912 Len=0 SLE=1 SRE=409 15319 146.969953 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK (text/html) 16943 158.964572 client server HTTP [TCP Retransmission] GET /... HTTP/1.0 16944 158.964609 server client TCP [TCP Dup ACK 15319#1] http > 28272 [ACK] Seq=2921 Ack=409 Win=6912 Len=0 SLE=1 SRE=409 16945 158.970635 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK (text/html) 20280 182.965032 client server HTTP [TCP Retransmission] GET /... HTTP/1.0 20281 182.965075 server client TCP [TCP Dup ACK 16945#1] http > 28272 [ACK] Seq=2921 Ack=409 Win=6912 Len=0 SLE=1 SRE=409 20282 182.972008 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK (text/html) Although the server keeps ack'ing the clients packets, the client keeps resubmitting. Example #2 -- client sends an HTTP POST request. Server processes it, and returns status code 200. Client never ack's, and server will resubmit a few times before giving up. Funny: Both client and server resubmit packets in the same time frame. Neither sees the other's ACK. TCP packet capture: No. Time Source Dest Proto Info 10782 105.461218 client server TCP 27549 > http [SYN] Seq=0 Win=5840 Len=0 MSS=1460 WS=2 10783 105.461281 server client TCP http > 27549 [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0 MSS=1460 WS=7 10784 105.477698 client server TCP 27549 > http [ACK] Seq=1 Ack=1 Win=5840 Len=0 10785 105.477723 client server HTTP [TCP Previous segment lost] Continuation or non-HTTP traffic 10786 105.477732 server client TCP [TCP Window Update] http > 27549 [ACK] Seq=1 Ack=1 Win=5888 Len=0 SLE=1461 SRE=2024 10787 105.477740 client server HTTP [TCP Out-Of-Order] POST /... HTTP/1.1 (application/x-www-form-urlencoded) 10788 105.477745 server client TCP http > 27549 [ACK] Seq=1 Ack=2024 Win=8832 Len=0 10801 105.497889 server client HTTP HTTP/1.1 200 OK 10802 105.497899 server client TCP http > 27549 [FIN, ACK] Seq=502 Ack=2024 Win=8832 Len=0 11034 108.477864 client server HTTP [TCP Retransmission] POST /... HTTP/1.1 (application/x-www-form-urlencoded) 11035 108.477870 server client TCP [TCP Dup ACK 10802#1] http > 27549 [ACK] Seq=503 Ack=2024 Win=8832 Len=0 SLE=1 SRE=1461 11044 108.495758 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK 11792 114.477977 client server HTTP [TCP Retransmission] POST /... HTTP/1.1 (application/x-www-form-urlencoded) 11793 114.478018 server client TCP [TCP Dup ACK 11044#1] http > 27549 [ACK] Seq=503 Ack=2024 Win=8832 Len=0 SLE=1 SRE=1461 11794 114.496111 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK 12662 126.496788 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK 15787 150.498155 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK 22195 198.500891 server client HTTP [TCP Retransmission] HTTP/ 1.1 200 OK --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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