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nodemcu-firmware/docs/en/modules/net.md

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net Module

Since Origin / Contributor Maintainer Source
2014-12-22 Zeroday Zeroday net.c

Constants

Constants to be used in other functions: net.TCP, net.UDP

net.createConnection()

Creates a client.

Syntax

net.createConnection(type, secure)

Parameters

  • type net.TCP or net.UDP
  • secure 1 for encrypted, 0 for plain

Returns

net.socket sub module

Example

net.createConnection(net.UDP, 0)

See also

net.createServer()

net.createServer()

Creates a server.

Syntax

net.createServer(type, timeout)

Parameters

  • type net.TCP or net.UDP
  • timeout for a TCP server timeout is 1~28'800 seconds (for an inactive client to be disconnected)

Returns

net.server sub module

Example

net.createServer(net.TCP, 30) -- 30s timeout

See also

net.createConnection()

net.server Module

net.server:close()

Closes the server.

Syntax

net.server.close()

Parameters

none

Returns

nil

Example

-- creates a server
sv = net.createServer(net.TCP, 30)
-- closes the server
sv:close()

See also

net.createServer()

net.server:listen()

Listen on port from IP address.

Syntax

net.server.listen(port,[ip],function(net.socket))

Parameters

  • port port number
  • ip IP address string, can be omitted
  • function(net.socket) callback function, pass to caller function as param if a connection is created successfully

Returns

nil

Example

 -- 30s time out for a inactive client
sv = net.createServer(net.TCP, 30)
-- server listens on 80, if data received, print data to console and send "hello world" back to caller
sv:listen(80, function(c)
  c:on("receive", function(c, pl) 
    print(pl)
  end)
  c:send("hello world")
end)

See also

net.createServer()

net.socket Module

net.socket:close()

Closes socket.

Syntax

close()

Parameters

none

Returns

nil

See also

net.createServer()

net.socket:connect()

Connect to a remote server.

Syntax

connect(port, ip|domain)

Parameters

  • port port number
  • ip IP address or domain name string

Returns

nil

See also

net.socket:on()

net.socket:dns()

Provides DNS resolution for a hostname.

Syntax

dns(domain, function(net.socket, ip))

Parameters

  • domain domain name
  • function(net.socket, ip) callback function. The first parameter is the socket, the second parameter is the IP address as a string.

Returns

nil

Example

sk = net.createConnection(net.TCP, 0)
sk:dns("www.nodemcu.com", function(conn, ip) print(ip) end)
sk = nil

See also

net.createServer()

net.socket:hold()

Throttle data reception by placing a request to block the TCP receive function. This request is not effective immediately, Espressif recommends to call it while reserving 5*1460 bytes of memory.

Syntax

hold()

Parameters

none

Returns

nil

See also

net.socket:unhold()

net.socket:on()

Register callback functions for specific events.

Syntax

on(event, function())

Parameters

  • event string, which can be "connection", "reconnection", "disconnection", "receive" or "sent"
  • function(net.socket[, string]) callback function. The first parameter is the socket. If event is "receive", the second parameter is the received data as string.

Returns

nil

Example

srv = net.createConnection(net.TCP, 0)
srv:on("receive", function(sck, c) print(c) end)
srv:connect(80,"192.168.0.66")
srv:on("connection", function(sck, c)
  -- Wait for connection before sending.
  sck:send("GET / HTTP/1.1\r\nHost: 192.168.0.66\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")
end)

See also

net.socket:send()

Sends data to server.

Syntax

send(string[, function(sent)])

sck:send(data, fnA) is functionally equivalent to sck:send(data) sck:on("sent", fnA).

Parameters

  • string data in string which will be sent to server
  • function(sent) callback function for sending string

Returns

nil

Note

Multiple consecutive send() calls aren't guaranteed to work (and often don't) as network requests are treated as separate tasks by the SDK. Instead, subscribe to the "sent" event on the socket and send additional data (or close) in that callback. See #730 for details.

Example

srv = net.createServer(net.TCP)
srv:listen(80, function(conn)
  conn:on("receive", function(sck, req)
    local response = {}

    -- if you're sending back HTML over HTTP you'll want something like this instead
    -- local response = {"HTTP/1.0 200 OK\r\nServer: NodeMCU on ESP8266\r\nContent-Type: text/html\r\n\r\n"}

    response[#response + 1] = "lots of data"
    response[#response + 1] = "even more data"
    response[#response + 1] = "e.g. content read from a file"
    
	 -- sends and removes the first element from the 'response' table
    local function send()
      if #response > 0
        then sck:send(table.remove(response, 1))
      else
        sck:close()
      end
    end

    -- triggers the send() function again once the first chunk of data was sent
    sck:on("sent", send)
    
    send()
  end)
end)

If you do not or can not keep all the data you send back in memory at one time (remember that response is an aggregation) you may use explicit callbacks instead of building up a table like so:

sck:send(header, function() 
  local data1 = "some large chunk of dynamically loaded data"
  sck:send(data1, function()
    local data2 = "even more dynamically loaded data"
    sck:send(data2, function() 
      sck:close()
    end)
  end)
end)

See also

net.socket:on()

net.socket:unhold()

Unblock TCP receiving data, i.e. undo hold().

Syntax

unhold()

Parameters

none

Returns

nil

See also

net.socket:hold()

net.dns Module

net.dns.getdnsserver()

Gets the IP address of the DNS server used to resolve hostnames.

Syntax

net.dns.getdnsserver(dns_index)

Parameters

dns_index which DNS server to get (range 0~1)

Returns

IP address (string) of DNS server

Example

print(net.dns.getdnsserver(0)) -- 208.67.222.222
print(net.dns.getdnsserver(1)) -- nil

net.dns.setdnsserver("8.8.8.8", 0)
net.dns.setdnsserver("192.168.1.252", 1)

print(net.dns.getdnsserver(0)) -- 8.8.8.8
print(net.dns.getdnsserver(1)) -- 192.168.1.252

See also

net.dns:setdnsserver()

net.dns.resolve()

Resolve a hostname to an IP address. Doesn't require a socket like net.socket.dns().

Syntax

net.dns.resolve(host, function(ip))

Parameters

  • host hostname to resolve
  • function(sk, ip) callback called when the name was resolved. Don't use sk, it's a socket used internally to resolve the hostname.

Returns

nil

Example

net.dns.resolve("www.google.com", function(sk, ip)
    if (ip == nil) then print("DNS fail!") else print(ip) end
end)

See also

net.socket:dns()

net.dns.setdnsserver()

Sets the IP of the DNS server used to resolve hostnames. Default: resolver1.opendns.com (208.67.222.222). You can specify up to 2 DNS servers.

Syntax

net.dns.setdnsserver(dns_ip_addr, dns_index)

Parameters

  • dns_ip_addr IP address of a DNS server
  • dns_index which DNS server to set (range 0~1). Hence, it supports max. 2 servers.

Returns

nil

See also

net.dns:getdnsserver()

net.cert Module

This controls certificate verification when SSL is in use.

net.cert.verify()

Controls the vertificate verification process when the Nodemcu makes a secure connection.

Syntax

net.cert.verify(enable)

net.cert.verify(pemdata)

Parameters

  • enable A boolean which indicates whether verification should be enabled or not. The default at boot is false.
  • pemdata A string containing the CA certificate to use for verification.

Returns

true if it worked.

Can throw a number of errors if invalid data is supplied.

Example

Make a secure https connection and verify that the certificate chain is valid.

net.cert.verify(true)
http.get("https://example.com/info", nil, function (code, resp) print(code, resp) end)

Load a certificate into the flash chip and make a request. This is the startssl root certificate. They provide free certificates.

net.cert.verify([[
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
]])

http.get("https://pskreporter.info/gen404", nil, function (code, resp) print(code, resp) end)

Notes

The certificate needed for verification is stored in the flash chip. The net.cert.verify call with true enables verification against the value stored in the flash.

The certificate can be loaded into the flash chip in two ways -- one at firmware build time, and the other at initial boot of the firmware. In order to load the certificate at build time, just place a file containing the CA certificate (in PEM format) at server-ca.crt in the root of the nodemcu-firmware build tree. The build scripts will incorporate this into the resulting firmware image.

The alternative approach is easier for development, and that is to supply the PEM data as a string value to net.cert.verify. This will store the certificate into the flash chip and turn on verification for that certificate. Subsequent boots of the nodemcu can then use net.cert.verify(true) and use the stored certificate.