I am using stunnel4 to build a secure connection between two ubuntu hosts. One of the hosts (sender) will send "hello world" to another host (receiver).
When I am using tcpdump in receiver to capture the packets sending from sender, I find out that one of the packets contains "hello world" in plaintext. From my understanding, stunnel will encrypt the content of "hello world" if everything is correct, so I shouldn't be able to see "hello world" in plaintext among any incoming packets. Any ideas about what is going wrong here?
Here I will put my stunnel.config for your reference:
cert = /home/ubuntu/client_server/stunnel.pem
key = /home/ubuntu/client_server/stunnel.key
debug = 7
output = /home/ubuntu/client_server/stunnel.log
socket = l:TCP_NODELAY=1
socket = r:TCP_NODELAY=1
options = ALL
[services]
accept = 6667
connect = some_ip_address:6666
TIMEOUTclose = 0