这里是有效连接的TCPdump。我使用ws端口5678，Ubuntu上的Apache 2.4.18和java.net.ServerSocket。
tcpdump -s 0 -A -vv'tcp端口5678'
09:48:51.736334 IP (tos 0x30, ttl 123, id 16157, offset 0, flags [DF], proto TCP (6), length 52)
188.146.240.28.nat.umts.dynamic.t-mobile.pl.13437 > mydydomain.eu.5678: Flags [S], cksum 0xaefc (correct), seq 886355024, win 64240, options [mss 1344,nop,wscale 8,nop,nop,sackOK], length 0
E0.4?.@.{........w4.4}..4..P...............@........
09:48:51.736544 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 52)
mydydomain.eu.5678 > 188.146.240.28.nat.umts.dynamic.t-mobile.pl.13437: Flags [S.], cksum 0x91ed (incorrect -> 0xff08), seq 1365829349, ack 886355025, win 29200, options [mss 1460,nop,nop,sackOK,nop,wscale 9], length 0
E..4..@.@....w4.......4}Qh..4..Q..r................
09:48:51.765802 IP (tos 0x30, ttl 123, id 16158, offset 0, flags [DF], proto TCP (6), length 40)
188.146.240.28.nat.umts.dynamic.t-mobile.pl.13437 > mydydomain.eu.5678: Flags [.], cksum 0xb0ec (correct), seq 1, ack 1, win 257, length 0
E0.(?.@.{........w4.4}..4..QQh..P.......ss (sc
如您所见，此处的握手握手进展顺利，而在另一台设备上，则无响应。
09:45:20.998134 IP (tos 0x48, ttl 248, id 2, offset 0, flags [DF], proto TCP (6), length 44)
ip-37-248-253-252.a2mobile.pl.8065 > mydydomain.eu.5678: Flags [S], cksum 0x8f11 (correct), seq 422071, win 23040, options [mss 1360], length 0
EH.,..@...yu%....w4.......p.....`.Z........P.$
09:45:23.715991 IP (tos 0x48, ttl 248, id 3, offset 0, flags [DF], proto TCP (6), length 44)
ip-37-248-253-252.a2mobile.pl.8065 > mydydomain.eu.5678: Flags [S], cksum 0x8f11 (correct), seq 422071, win 23040, options [mss 1360], length 0
EH.,..@...yt%....w4.......p.....`.Z........P..
09:45:26.136562 IP (tos 0x48, ttl 248, id 2, offset 0, flags [DF], proto TCP (6), length 44)
ip-37-248-253-252.a2mobile.pl.8065 > mydydomain.eu.5678: Flags [S], cksum 0x8f11 (correct), seq 422071, win 23040, options [mss 1360], length 0
EH.,..@...yu%....w4.......p.....`.Z........PJ.
如果有人可以给mi一些建议，我应该检查些什么来解决问题。
谢谢。
编辑。 通过ngrok tunel，G510模块可以很好地连接，但是我不想使用它。