Online Play

Online Play is a functionality of the Nintendo 3DS to play games online with other people.

Connection

First a connection to nasc.nintendowifi.net is established and the resource /ac is requested with the POST method to get the actual address of the game server and a ticket for authentication on the game server.
A typical request to nasc.nintendowifi.net/ac has this format:

Header:

POST https://nasc.nintendowifi.net/ac HTTP/1.1
Host: nasc.nintendowifi.net
X-GameId: 00003200
User-Agent: CTR FPD/000F
Content-Type: application/x-www-form-urlencoded
Content-Type: application/x-www-form-urlencoded
Content-Length: 841

Body:

gameid=MDAwMDMyMDA%2A&sdkver=MDAwMDAw&titleid=MDAwNDAxMzAwMDAwMzIwMg%2A%2A&gamecd=LS0tLQ%2A%2A&gamever=MDAxNA%2A%2A&mediatype=MA%2A%2A&makercd=MDA%2A&unitcd=Mg%2A%2A&macadr=MTEyMjMzNDQ1NTY2&bssid=MTEyMjMzYWFiYmNj&apinfo=MDQ6MDAwMDAwMDAwMA%2A%2A&fcdcert=<base64 encoded fcdcert>&devname=<base64 encoded name of the console (utf-16)>&servertype=TDE%2A&fpdver=MDAwRg%2A%2A&devtime=MjEwMTAxMjAyNjAx&lang=MDE%2A&region=MDI%2A&csnum=<base64 encoded serial number of the 3DS system wihtout check number>&uidhmac=<base64 encoded of ?>&userid=<base64 encoded Nex [[Principal ID]]>&action=TE9HSU4%2A&ingamesn=

Key	Value	Value decoded	Notes
gameid	MDAwMDMyMDA*	00003200
sdkver	MDAwMDAw	000000
titleid	MDAwNDAxMzAwMDAwMzIwMg**	0004013000003202
gamecd	LS0tLQ**	----
gamever	MDAxNA**	0014
mediatype	MA**	0
makercd	MDA*	00
unitcd	Mg**	2
macadr	MTEyMjMzNDQ1NTY2	112233445566	MAC address of the console. Only the digits
bssid	MTEyMjMzYWFiYmNj	112233aabbcc
apinfo	MDQ6MDAwMDAwMDAwMA**	04:0000000000
fcdcert
devname			Name of the console in UTF-16
servertype	TDE*	L1
fpdver	MDAwRg**	000F
devtime	MjEwMTAxMDkyMDMx	210101092031
lang	MDE*	01
region	MDE*	01
csnum	Q0VGMTIzNDU2Nzg*	CEF12345678	Serial number of the device without the check digit
uidhmac	MGFmODZmYmQ*	0af86fbd
userid	MTIzNDU2Nzg5MA**	1234567890	Nex Principal ID
action	TE9HSU4*	LOGIN
ingamesn	empty	empty

Typical response to the above request:

Header:

HTTP/1.1 200 OK
NODE: pd42wfiap02
Content-Type: text/plain;charset=ISO-8859-1
Content-Length: 252
Date: Fri, 01 Jan 2021 09:20:55 GMT
Server: Nintendo Wii (http)

Body:

locator=MzQuMjExLjIzNS4xMzU6NjAwMDA*&retry=MA**&returncd=MDAx&token=<Token for authentication on the game server>&datetime=MjAyMTAxMDEwOTIwNTU*

Key	Value	Value decoded	Notes
locator	MzQuMjExLjIzNS4xMzU6NjAwMDA*	34.211.235.135:60000	IP address and port of the game server
retry	MA**	0
returncd	MDAx	001
token			Token for authentication on the game server. This token cannot be verified by the Nintendo 3DS
datetime	MjAyMTAxMDEwOTIwNTU*	20210101092055