Server-client handshake fails

[neliavaal]

server:
./udp2raw_amd64 -s -lserver_public_IP:61111 -r server_public_IP:514 -k "passwd_S123" --raw-mode faketcp -a

client
./udp2raw_arm -c -l192.168.1.1:5555 -rserver_public_IP:61111 -k "passwd_S123" --raw-mode faketcp -a

server:

./udp2raw_amd64 -s -lserver_public_IP:61111 -r server_public_IP:514 -k "passwd_S123" --raw-mode faketcp -a
[2025-10-14 19:47:22][INFO]argc=10 ./udp2raw_amd64 -s -lserver_public_IP:61111 -r server_public_IP:514 -k passwd_S123 --raw-mode faketcp -a 
[2025-10-14 19:47:22][INFO]parsing address: server_public_IP:61111
[2025-10-14 19:47:22][INFO]its an ipv4 adress
[2025-10-14 19:47:22][INFO]ip_address is {server_public_IP}, port is {61111}
[2025-10-14 19:47:22][INFO]parsing address: server_public_IP:514
[2025-10-14 19:47:22][INFO]its an ipv4 adress
[2025-10-14 19:47:22][INFO]ip_address is {server_public_IP}, port is {514}
[2025-10-14 19:47:22][INFO]important variables: log_level=4:INFO raw_mode=faketcp cipher_mode=aes128cbc auth_mode=md5 key=passwd_S123 local_addr=server_public_IP:61111 remote_addr=server_public_IP:514 socket_buf_size=1048576 
[2025-10-14 19:47:22][WARN]you can run udp2raw with non-root account for better security. check README.md in repo for more info.
[2025-10-14 19:47:22][INFO]remote_ip=[server_public_IP], make sure this is a vaild IP address
[2025-10-14 19:47:22][INFO]const_id:117fecd0
[2025-10-14 19:47:22][INFO]run_command iptables -N udp2rawDwrW_117fecd0_C0
[2025-10-14 19:47:22][INFO]run_command iptables -F udp2rawDwrW_117fecd0_C0
[2025-10-14 19:47:22][INFO]run_command iptables -I udp2rawDwrW_117fecd0_C0 -j DROP
[2025-10-14 19:47:22][INFO]run_command iptables -I INPUT -d server_public_IP -p tcp -m tcp --dport 61111 -j udp2rawDwrW_117fecd0_C0
[2025-10-14 19:47:22][WARN]auto added iptables rules
[2025-10-14 19:47:22][INFO]now listening at server_public_IP:61111
[2025-10-14 19:47:23][INFO][my_public_IP:14534]received syn,sent syn ack back
[2025-10-14 19:47:23][INFO][my_public_IP:14534]got packet from a new ip
[2025-10-14 19:47:23][INFO][my_public_IP:14534]created new conn,state: server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:23][INFO][my_public_IP:14534]changed state to server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:25][INFO][my_public_IP:14534]changed state to server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:26][INFO][my_public_IP:14534]changed state to server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:27][INFO][my_public_IP:14534]changed state to server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:28][INFO][my_public_IP:14534]changed state to server_handshake1,my_id is 4f4e0e10
[2025-10-14 19:47:29][INFO][my_public_IP:32246]received syn,sent syn ack back
[2025-10-14 19:47:29][INFO][my_public_IP:32246]got packet from a new ip
[2025-10-14 19:47:29][INFO][my_public_IP:32246]created new conn,state: server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:29][INFO][my_public_IP:32246]changed state to server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:30][INFO][my_public_IP:32246]changed state to server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:31][INFO][my_public_IP:32246]changed state to server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:33][INFO][my_public_IP:32246]changed state to server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:34][INFO][my_public_IP:32246]changed state to server_handshake1,my_id is 5b038ab4
[2025-10-14 19:47:35][INFO][my_public_IP:63433]received syn,sent syn ack back
[2025-10-14 19:47:35][INFO][my_public_IP:63433]got packet from a new ip
[2025-10-14 19:47:35][INFO][my_public_IP:63433]created new conn,state: server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:35][INFO][my_public_IP:63433]changed state to server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:36][INFO][my_public_IP:14534]inactive conn cleared 
[2025-10-14 19:47:36][INFO][my_public_IP:63433]changed state to server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:37][INFO][my_public_IP:63433]changed state to server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:38][INFO][my_public_IP:63433]changed state to server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:39][INFO][my_public_IP:63433]changed state to server_handshake1,my_id is ba500ea5
[2025-10-14 19:47:40][INFO][my_public_IP:12471]received syn,sent syn ack back
[2025-10-14 19:47:40][INFO][my_public_IP:12471]got packet from a new ip
[2025-10-14 19:47:40][INFO][my_public_IP:12471]created new conn,state: server_handshake1,my_id is ba971c29
[2025-10-14 19:47:40][INFO][my_public_IP:12471]changed state to server_handshake1,my_id is ba971c29
[2025-10-14 19:47:40][INFO][my_public_IP:32246]inactive conn cleared 
[2025-10-14 19:47:41][INFO][my_public_IP:12471]changed state to server_handshake1,my_id is ba971c29
^C[2025-10-14 19:47:42][INFO]epoll interrupted by signal,continue

[2025-10-14 19:47:42][INFO]run_command iptables -D INPUT -d server_public_IP -p tcp -m tcp --dport 61111 -j udp2rawDwrW_117fecd0_C0
[2025-10-14 19:47:42][INFO]run_command iptables -F udp2rawDwrW_117fecd0_C0
[2025-10-14 19:47:42][INFO]run_command iptables -X udp2rawDwrW_117fecd0_C0

client:

./udp2raw_arm -c -l192.168.1.1:5555  -rserver_public_IP:61111 
 -k "passwd_S123" --raw-mode faketcp -a
[2025-10-14 19:48:37][INFO]argc=9 ./udp2raw_arm -c -l192.168.1.1:5555 -rserver_public_IP:61111 -k passwd_S123 --raw-mode faketcp -a 
[2025-10-14 19:48:37][INFO]parsing address: 192.168.1.1:5555
[2025-10-14 19:48:37][INFO]its an ipv4 adress
[2025-10-14 19:48:37][INFO]ip_address is {192.168.1.1}, port is {5555}
[2025-10-14 19:48:37][INFO]parsing address: server_public_IP:61111
[2025-10-14 19:48:37][INFO]its an ipv4 adress
[2025-10-14 19:48:37][INFO]ip_address is {server_public_IP}, port is {61111}
[2025-10-14 19:48:37][INFO]important variables: log_level=4:INFO raw_mode=faketcp cipher_mode=aes128cbc auth_mode=md5 key=passwd_S123 local_addr=192.168.1.1:5555 remote_addr=server_public_IP:61111 socket_buf_size=1048576 
[2025-10-14 19:48:37][WARN]you can run udp2raw with non-root account for better security. check README.md in repo for more info.
[2025-10-14 19:48:37][INFO]remote_ip=[server_public_IP], make sure this is a vaild IP address
[2025-10-14 19:48:37][INFO]const_id:647ab9f8
[2025-10-14 19:48:37][INFO]run_command iptables -N udp2rawDwrW_647ab9f8_C0
[2025-10-14 19:48:37][INFO]run_command iptables -F udp2rawDwrW_647ab9f8_C0
[2025-10-14 19:48:37][INFO]run_command iptables -I udp2rawDwrW_647ab9f8_C0 -j DROP
[2025-10-14 19:48:37][INFO]run_command iptables -I INPUT -s server_public_IP -p tcp -m tcp --sport 61111 -j udp2rawDwrW_647ab9f8_C0
[2025-10-14 19:48:37][WARN]auto added iptables rules
[2025-10-14 19:48:37][INFO]source_addr is now 10.66.66.2
[2025-10-14 19:48:37][INFO]using port 14534
[2025-10-14 19:48:37][INFO]state changed from client_idle to client_tcp_handshake
[2025-10-14 19:48:37][INFO](re)sent tcp syn
[2025-10-14 19:48:37][INFO]state changed from client_tcp_handshake to client_handshake1
[2025-10-14 19:48:37][INFO](re)sent handshake1
[2025-10-14 19:48:39][INFO](re)sent handshake1
[2025-10-14 19:48:40][INFO](re)sent handshake1
[2025-10-14 19:48:41][INFO](re)sent handshake1
[2025-10-14 19:48:42][INFO](re)sent handshake1
[2025-10-14 19:48:43][INFO]state back to client_idle from client_handshake1
[2025-10-14 19:48:43][INFO]source_addr is now 10.66.66.2
[2025-10-14 19:48:43][INFO]using port 32246
[2025-10-14 19:48:43][INFO]state changed from client_idle to client_tcp_handshake
[2025-10-14 19:48:43][INFO](re)sent tcp syn
[2025-10-14 19:48:43][INFO]state changed from client_tcp_handshake to client_handshake1
[2025-10-14 19:48:43][INFO](re)sent handshake1
[2025-10-14 19:48:44][INFO](re)sent handshake1
[2025-10-14 19:48:45][INFO](re)sent handshake1
[2025-10-14 19:48:47][INFO](re)sent handshake1
[2025-10-14 19:48:48][INFO](re)sent handshake1
[2025-10-14 19:48:48][INFO]state back to client_idle from client_handshake1
[2025-10-14 19:48:49][INFO]source_addr is now 10.66.66.2
[2025-10-14 19:48:49][INFO]using port 63433
[2025-10-14 19:48:49][INFO]state changed from client_idle to client_tcp_handshake
[2025-10-14 19:48:49][INFO](re)sent tcp syn
[2025-10-14 19:48:49][INFO]state changed from client_tcp_handshake to client_handshake1
[2025-10-14 19:48:49][INFO](re)sent handshake1
[2025-10-14 19:48:50][INFO](re)sent handshake1
[2025-10-14 19:48:51][INFO](re)sent handshake1
[2025-10-14 19:48:52][INFO](re)sent handshake1
[2025-10-14 19:48:53][INFO](re)sent handshake1
[2025-10-14 19:48:54][INFO]state back to client_idle from client_handshake1
[2025-10-14 19:48:54][INFO]source_addr is now 10.66.66.2
[2025-10-14 19:48:54][INFO]using port 12471
[2025-10-14 19:48:54][INFO]state changed from client_idle to client_tcp_handshake
[2025-10-14 19:48:54][INFO](re)sent tcp syn
[2025-10-14 19:48:54][INFO]state changed from client_tcp_handshake to client_handshake1
[2025-10-14 19:48:54][INFO](re)sent handshake1
[2025-10-14 19:48:55][INFO](re)sent handshake1
[2025-10-14 19:48:57][INFO](re)sent handshake1
^C[2025-10-14 19:48:57][INFO]got sigint, exit
[2025-10-14 19:48:57][INFO]run_command iptables -D INPUT -s server_public_IP -p tcp -m tcp --sport 61111 -j udp2rawDwrW_647ab9f8_C0
[2025-10-14 19:48:57][INFO]run_command iptables -F udp2rawDwrW_647ab9f8_C0
[2025-10-14 19:48:57][INFO]run_command iptables -X udp2rawDwrW_647ab9f8_C0

UPD: it only happens with --raw-mode faketcp while using udp or icmp does allow to establish the connection

[iopq]

You need to open the TCP port on the server, enable ip_forwarding, disable rp_filter