Linux and SCO ppp, firewall issue?

I' m playng a little retrocomputing.
I have setup a virtual machine with SCO unix(3.2v4.2) on qemu
The machine start, the novell2000 card(ne2k_pci,ne2k_isa) unfortunately not,probably driver issue.
So I try the slirp with this procedure
On SCO

    netconfig
    add chain..sl ..etc

On linux

   slattach -s 19200 -d -p slip /dev/pts/2
    ifconfig sl0 192.168.7.1 dstaddr 192.168.7.2 netmask 255.255.255.252 mtu 296 up

At reboot: ping work,telnet work,but when I try a ftp transfer of a little file(7m) the transfer is blocked.
So I have tried PPP and pppd
On SCO

    netconfig
    remove chain sl0
    add chain ppp
    reboot

On linux

    pppd -detach debug local noauth passive lock 192.168.7.1:192.168.7.2 netmask 255.255.255.0 /dev/pts/2 9600 connect /usr/sbin/chat -s -v login:--login: nppp word: nppppassword

The connection is up,but telnet and ftp won't start
Seems blocking by firewall,this is my firewall config

 #!/bin/sh
    
    # We need this for redirection
    echo 1 > /proc/sys/net/ipv4/ip_forward
    
    firewall_start() {
    # Clean
    iptables -F
    iptables -X
    iptables -Z
    iptables -t nat -F
    iptables -t nat -X
    iptables -t nat -Z
    iptables -t mangle -F
    iptables -t mangle -X
    iptables -t mangle -Z
    
    # Default policy
    #iptables -P PREROUTING  ACCEPT
    #iptables -P OUTPUT  ACCEPT
    #iptables -P POSTROUTING  ACCEPT
    #iptables -P INPUT ACCEPT
    #iptables -P FORWARD ACCEPT
    
    # Firewall rules INPUT
    iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
    iptables -A INPUT -i lo -j ACCEPT
    
    # Ssh 
    iptables -A INPUT -p tcp --dport 22 -j ACCEPT
    
    # Ftp
    iptables -A INPUT -s 192.168.178.0/24 -p tcp --dport 20:21 -j ACCEPT
    
    # Rules for dnsmasq
    iptables -A INPUT -i virbr0 -p tcp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr0 -p udp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr0 -p tcp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr0 -p udp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr1 -p tcp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr1 -p udp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr1 -p tcp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr1 -p udp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr2 -p tcp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr2 -p udp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr2 -p tcp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr2 -p udp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr3 -p tcp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr3 -p udp --dport 67 -j ACCEPT
    iptables -A INPUT -i virbr3 -p tcp --dport 53 -j ACCEPT
    iptables -A INPUT -i virbr3 -p udp --dport 53 -j ACCEPT
    
    # Icmp
    iptables -A INPUT -p icmp --icmp-type 0 -j ACCEPT
    iptables -A INPUT -p icmp --icmp-type 8 -j ACCEPT
    
    # Virbr NAT
    iptables -A FORWARD -i virbr0 -o wlan0 -j ACCEPT
    iptables -A FORWARD -i wlan0 -o virbr0 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i virbr1 -o wlan0 -j ACCEPT
    iptables -A FORWARD -i wlan0 -o virbr1 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i virbr2 -o wlan0 -j ACCEPT
    iptables -A FORWARD -i wlan0 -o virbr2 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i virbr2 -o tun0 -j ACCEPT
    iptables -A FORWARD -i tun0 -o virbr2 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i virbr3 -o usb0 -j ACCEPT
    iptables -A FORWARD -i usb0 -o virbr3 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -A FORWARD -i ppp0 -o wlan0 -j ACCEPT
    iptables -A FORWARD -i wlan0 -o ppp0 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
    iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
    iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
    iptables -t nat -A POSTROUTING -o usb0 -j MASQUERADE
    
    # Log
    #iptables -N LOGGING
    #iptables -A INPUT -j LOGGING
    #iptables -A FORWARD -j LOG
    #iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables-Dropped: " --log-level 4
    #iptables -A LOGGING -j DROP
    
    #Final rules
    iptables -A INPUT -j REJECT --reject-with icmp-host-prohibited
    iptables -A FORWARD -j REJECT --reject-with icmp-host-prohibited
    }
    
    firewall_stop() {
    # Clean
    iptables -F
    iptables -X
    iptables -Z
    iptables -t nat -F
    iptables -t nat -X
    iptables -t nat -Z
    iptables -t mangle -F
    iptables -t mangle -X
    iptables -t mangle -Z
    }
    
    
    firewall_restart() {
    firewall_stop
    firewall_start
    }
    
    case "$1" in
    'start')
      firewall_start
      ;;
    'stop')
      firewall_stop
      ;;
    'restart')
      firewall_restart
      ;;
    *)
      echo "usage $0 start|stop|restart"
    esac

Any suggestion?Thanks

tcp is not included with SCO 3.2.4. You need to also install tcp 3.2.1 which was a separately purchased item.

You could use kermit C-Kermit Binaries to transfer the files, or uucp.
You also haven't said which direction the copy is going in, and whether you are pulling the file, or pushing it.

tcp is installed
otherwise I cannot try the ne2k card and the ppp