• To develop 'target' application on host

• Ubuntu OS (on account of using TAP interface)
• gcc

Get in lwip_contrib/contrib/ports/unix/minimal directory.

• Build:
  • make
• Run:
  • sudo ./echop

When it starts running, it will create tap1 interface and then it will link the tap1 interface to LwIP TCP/IP Stack.
Thanks to this 'link', the end user will have the chance to run network applications on the same machine but with different IP Addresses.

• According to your network settings, you need to change the IP Address / GW Address / Subnet mask of TCP/IP Stack by changing the parameters mentioned below (in main.c):
  IP4_ADDR(&gw, 192,168,1,1);
  IP4_ADDR(&ipaddr, 192,168,1,20);
  IP4_ADDR(&netmask, 255,255,255,0);
  

• You should see messages on stdout like the ones below, when it starts running successfully:
  

  Host at 192.168.1.20 mask 255.255.255.0 gateway 192.168.1.1
  TCP/IP initialized.
  SNMP private MIB start, detecting sensors.
  Applications started.
  

• When you type "ip link" command in the terminal you should see tap1 interface up as mentioned below (Your MAC Address instead of NO):
  

  tap1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 1000
  link/ether NO:NO:NO:NO:NO:NO brd ff:ff:ff:ff:ff:ff
  

• Communication Test:

  • To test TCP communication type the command mentioned below and then you will see the messages twice due to 'echo' server:
    nc -l 192.168.1.20(Your IP Address) 45678
    
  • To test UDP communication type the command mentioned below and then you will see the messages twice due to 'echo' server:
    nc -u -l 192.168.1.20(Your IP Address) 7