Problem with several devices on the same port

I added one tracker to server. Protocol is TK103. I use port 20300.
This tracker worked fine until i added second...
After i added second tracker - first stopped writing coordinates.

Log:

2015-09-22 11:14:55 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344250303030303030323730343332353131363448534f29
2015-09-22 11:14:55 DEBUG: [14B274B4: 20300 > 46.211.189.217] HEX: 283032373034333235313136344150303148534f29
2015-09-22 11:15:08 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333733374e30333332362e31333634453030302e33303831343332302e3030303030303030303030304c303030303030303029
2015-09-22 11:15:08  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:14:32 EEST 2015, lat: 47.972895, lon: 33.435606666666665, speed: 0.1619871, course: 0.0
2015-09-22 11:15:28 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333733354e30333332362e31323930453030302e39303831343532302e3030303030303030303030304c303030303030303029
2015-09-22 11:15:28  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:14:52 EEST 2015, lat: 47.97289166666667, lon: 33.43548333333333, speed: 0.48596130000000004, course: 0.0
2015-09-22 11:15:47 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333733364e30333332362e31323635453030302e32303831353132302e3030303030303030303030304c303030303030303029
2015-09-22 11:15:48  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:15:12 EEST 2015, lat: 47.97289333333333, lon: 33.43544166666667, speed: 0.10799140000000002, course: 0.0
2015-09-22 11:16:07 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333734344e30333332362e31323534453030302e37303831353332302e3030303030303030303030304c303030303030303029
2015-09-22 11:16:08  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:15:32 EEST 2015, lat: 47.97290666666667, lon: 33.43542333333333, speed: 0.37796989999999997, course: 0.0
2015-09-22 11:16:27 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333735304e30333332362e31323236453030302e36303831353532302e3030303030303030303030304c303030303030303029
2015-09-22 11:16:28  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:15:52 EEST 2015, lat: 47.97291666666667, lon: 33.43537666666667, speed: 0.3239742, course: 0.0
2015-09-22 11:16:47 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333737304e30333332362e31313737453030302e31303831363132302e3030303030303030303030304c303030303030303029
2015-09-22 11:16:47  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:16:12 EEST 2015, lat: 47.97295, lon: 33.435294999999996, speed: 0.05399570000000001, course: 0.0
2015-09-22 11:17:07 DEBUG: [14B274B4: 20300 < 46.211.189.217] HEX: 283032373034333235313136344252303031353039323241343735382e333738344e30333332362e31313635453030302e34303831363332302e3030303030303030303030304c303030303030303029
2015-09-22 11:17:07  INFO: [14B274B4] id: 2, time: Tue Sep 22 11:16:32 EEST 2015, lat: 47.972973333333336, lon: 33.435275, speed: 0.21598280000000003, course: 0.0
2015-09-22 11:28:13  INFO: [861A9D7A] connected
2015-09-22 11:28:14 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333738324e30333332362e31323237453030312e32303831393137302e3030303030303030303030304c303030303030303029
2015-09-22 11:28:14  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:19:17 EEST 2015, lat: 47.97297, lon: 33.43537833333333, speed: 0.6479484, course: 0.0
2015-09-22 11:28:15 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324250303030303030323730343332353033373248534f29
2015-09-22 11:28:15 DEBUG: [861A9D7A: 20300 > 46.211.147.254] HEX: 283032373034333235303337324150303148534f29
2015-09-22 11:28:25 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333738324e30333332362e31323237453030312e32303831393137302e3030303030303030303030304c303030303030303029
2015-09-22 11:28:25  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:19:17 EEST 2015, lat: 47.97297, lon: 33.43537833333333, speed: 0.6479484, course: 0.0
2015-09-22 11:28:45 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333736364e30333332362e31333633453030302e36303832383038302e3030303030303030303030304c303030303030303029
2015-09-22 11:28:45  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:28:08 EEST 2015, lat: 47.97294333333333, lon: 33.435605, speed: 0.3239742, course: 0.0
2015-09-22 11:29:05 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333737334e30333332362e31333533453030322e31303832383238302e3030303030303030303030304c303030303030303029
2015-09-22 11:29:05  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:28:28 EEST 2015, lat: 47.972955, lon: 33.435588333333335, speed: 1.1339097, course: 0.0
2015-09-22 11:29:25 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333736364e30333332362e31333339453030302e31303832383438302e3030303030303030303030304c303030303030303029
2015-09-22 11:29:25  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:28:48 EEST 2015, lat: 47.97294333333333, lon: 33.435565, speed: 0.05399570000000001, course: 0.0
2015-09-22 11:29:45 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333737324e30333332362e31323433453030302e33303832393038302e3030303030303030303030304c303030303030303029
2015-09-22 11:29:45  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:29:08 EEST 2015, lat: 47.972953333333336, lon: 33.435405, speed: 0.1619871, course: 0.0
2015-09-22 11:30:04 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333736304e30333332362e31323937453030302e35303832393238302e3030303030303030303030304c303030303030303029
2015-09-22 11:30:05  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:29:28 EEST 2015, lat: 47.97293333333333, lon: 33.435495, speed: 0.2699785, course: 0.0
2015-09-22 11:30:24 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333735304e30333332362e31333734453030302e36303832393438302e3030303030303030303030304c303030303030303029
2015-09-22 11:30:25  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:29:48 EEST 2015, lat: 47.97291666666667, lon: 33.43562333333333, speed: 0.3239742, course: 0.0
2015-09-22 11:30:44 DEBUG: [861A9D7A: 20300 < 46.211.147.254] HEX: 283032373034333235303337324252303031353039323241343735382e333737304e30333332362e31333036453030312e31303833303038302e3030303030303030303030304c303030303030303029
2015-09-22 11:30:44  INFO: [861A9D7A] id: 4, time: Tue Sep 22 11:30:08 EEST 2015, lat: 47.97295, lon: 33.43551, speed: 0.5939527000000001, course: 0.0

What i do wrong?

As far as I can see everything is decoded correctly. Your first device just stopped sending data.

I dont know where is the problem. When i added third device - second stopped writing coordinates too.
Where can i look a problem?

It sounds like some device side problem to me. Don't know why they stop sending data.

А вообще в протоколе TK103 предусмотрен ответ на hendshake сообщение?
Просто я настроил 6 трекеров подряд. Все работали нормально. Потом по одному начали отваливаться.
В логах ничего нет.

In general, the protocol provides TK103 hendshake response to a message?
I just set up six consecutive trackers. Everything worked fine. Then one by one began to fall off.
The logs empty.

Yes, Traccar server sends handshake response as expected (see your original log). Not sure what can be the issue. I guess you need to ask manufacturer or seller.

If you have protocol documentation, I can check for you if the handshake is correct.

I contacted with supplier. It seems it problem with tracker. Thank you for help.