Connection issue with external computer (terrain loading blocked)

Hi, I’m French, sorry in advance for my grammar. When I try to connect to my server with an external pc, the terrain loading remains blocked. I has open my ports and i can connect with filezilla on my server. So I think it’s not a issu whith my internet box configuration and my connection is good.
Can you help me please ?

That to me would seem more like a routing and/or firewall issue, not really sure how that’d be worked on/fixed, If you have ports forwarded and can successfully connect but chunks/terrain don’t load then it’s probably a routing or firewall issue where the connection is being dropped or throttled, or the server lagging very badly.

foremost, I disabled all ports with “iptables -P INPUT ACCEPT”, so it isn’t an issue with the firewall of the server, isn’t it ?

Well it can be one of (potentially) several firewalls, being the server (ruled out), router/modem/gateway, and ISP. Connections are made, but then dropped…wait actually do you remain connected with no chunks/terrain or do you time out/get disconnected? What also would be helpful is the server latest.log file when it happens to see if the server “can’t keep up” (aka is lagging) or if it is some other issue with routing. A way to test would be with direct connections and static IP assignments but that comes if the server’s latest.log isn’t of any help (indicates nothing as being wrong). You can find it in your server’s directory /var/games/minecraft/servers/[server]/logs/.