Problems with DNS in NodeMCU - esp8266

Question

I am trying to just make a connection from the ESP8266 and a test server like www.httpbin.org to get some data. I keep having problems in the connection.
I am using a very simple code that (excluding the obvious connection to the local WiFi) looks like:
net.dns.setdnsserver("8.8.8.8",1)
net.dns.resolve("httpbin.org", function(server_ip)
if (server_ip == nil) then print("DNS fail!") else
print(server_ip)
conn=net.createConnection(net.TCP, 0)
conn:on("receive", function(conn, payload)
print('\nReceived\n')
print(payload)
end )
conn:on("connection", function(conn, payload)
print('\nConnected')
conn:send("HTTP/1.1\r\n"
.."Host: httpbin.org/get\r\n"
.."Connection: keep-alive\r\n"
.."Accept: */*\r\n\r\n")
end)
conn:connect(80, server_ip)
end
end)
I get as result that the print(server_ip) returns
userdata: 3fff1b80
And the connection hangs (I never get any message printed). What am I doing wrong? Thanks.

Answer 1

You were nearly there. Try this:
net.dns.setdnsserver("8.8.8.8", 1)
net.dns.resolve("httpbin.org", function(sk, server_ip)
if (server_ip == nil) then print("DNS fail!") else
print(server_ip)
conn = net.createConnection(net.TCP, 0)
conn:on("receive", function(conn, payload)
print("Received: " .. payload)
end)
conn:on("connection", function(conn, payload)
print("Connected")
conn:send("GET /get HTTP/1.1\r\n"
.. "Host: httpbin.org\r\n"
.. "Connection: keep-alive\r\n"
.. "Accept: */*\r\n\r\n")
end)
conn:connect(80, server_ip)
end
end)
I changed two things:
as per the docs the callback for net.dns.resolve has 2 parameters (socket and IP address)
the HTTP headers were wrong:
host really is just the host
but the HTTP verb and the path were missing, it's GET /get HTTP/1.1
Of course you may just as well strip this down to:
conn = net.createConnection(net.TCP, 0)
conn:on("receive", function(conn, payload)
print("Received: " .. payload)
end)
conn:on("connection", function(conn, payload)
print("Connected")
conn:send("GET /get HTTP/1.1\r\n"
.. "Host: httpbin.org\r\n"
.. "Connection: keep-alive\r\n"
.. "Accept: */*\r\n\r\n")
end)
conn:connect(80, "httpbin.org")