how to use libminiupnpc to setup port forwarding

Question

I'd like to use libminiupnpc (github) to find devices and do TCP port forwarding/mapping. However, I cannot find a single decent document or example code that shows how to use the miniupnpc API.

Anyone know of a good document or example code that shows how to use this library?

What I have now is:

#include <miniupnpc/miniupnpc.h>
...
int error = 0;
UPNPDev *dev = upnpDiscover(2000, nullptr, nullptr, 0, 0, &error);

...which seems to correctly return information on my router:

2014-09-08 11:36:17.417132 debug  - UPnP ERROR: 0
2014-09-08 11:36:17.417394 debug  - UPnP device:
    url: http://192.168.1.1:5431/dyndev/uuid:207605a3-efd0-d0ef-a320-162376a3d04000
    st:  urn:schemas-upnp-org:device:InternetGatewayDevice:1
    buf: http://192.168.1.1:5431/dyndev/uuid:207605a3-efd0-d0ef-a320-162376a3d04000

Problem is other than upnpDiscover() it isn't obvious what needs to be called next.

You might be better off posting the same question to [the project's forum](http://miniupnp.tuxfamily.org/forum/) — simonc, Sep 09 '14 at 08:51
Note the forum is not active. There is about 1 post per month to it. My questions have (so far) gone unanswered on the forum. — Stéphane, Sep 11 '14 at 13:51

score 9 · Accepted Answer · answered Sep 11 '14 at 13:46

Miniupnp is not very well (or at all?) documented. Here is what I eventually figured out is required to add and list port mappings. I'll leave out error handling.

int error = 0;
struct UPNPDev *upnp_dev = upnpDiscover(
        2000    , // time to wait (milliseconds)
        nullptr , // multicast interface (or null defaults to 239.255.255.250)
        nullptr , // path to minissdpd socket (or null defaults to /var/run/minissdpd.sock)
        0       , // source port to use (or zero defaults to port 1900)
        0       , // 0==IPv4, 1==IPv6
        &error  ); // error condition

char lan_address[64];
struct UPNPUrls upnp_urls;
struct IGDdatas upnp_data;
int status = UPNP_GetValidIGD(upnp_dev, &upnp_urls, &upnp_data, lan_address, sizeof(lan_address));
// look up possible "status" values, the number "1" indicates a valid IGD was found

// get the external (WAN) IP address
char wan_address[64];
UPNP_GetExternalIPAddress(upnp_urls.controlURL, upnp_data.first.servicetype, wan_address);

// add a new TCP port mapping from WAN port 12345 to local host port 24680
error = UPNP_AddPortMapping(
            upnp_urls.controlURL,
            upnp_data.first.servicetype,
            "12345"     ,  // external (WAN) port requested
            "24680"     ,  // internal (LAN) port to which packets will be redirected
            lan_address , // internal (LAN) address to which packets will be redirected
            "FooBar server for XYZ", // text description to indicate why or who is responsible for the port mapping
            "TCP"       , // protocol must be either TCP or UDP
            nullptr     , // remote (peer) host address or nullptr for no restriction
            "86400"     ); // port map lease duration (in seconds) or zero for "as long as possible"

// list all port mappings
size_t index = 0;
while (true)
{
    char map_wan_port           [200] = "";
    char map_lan_address        [200] = "";
    char map_lan_port           [200] = "";
    char map_protocol           [200] = "";
    char map_description        [200] = "";
    char map_mapping_enabled    [200] = "";
    char map_remote_host        [200] = "";
    char map_lease_duration     [200] = ""; // original time, not remaining time :(

    error = UPNP_GetGenericPortMappingEntry(
                upnp_urls.controlURL            ,
                upnp_data.first.servicetype     ,
                std::to_string(index).c_str()   ,
                map_wan_port                    ,
                map_lan_address                 ,
                map_lan_port                    ,
                map_protocol                    ,
                map_description                 ,
                map_mapping_enabled             ,
                map_remote_host                 ,
                map_lease_duration              );

    if (error)
    {
        break; // no more port mappings available
    }

    std::cout << ....print out or do whatever you want with the map_* fields
}

Two useful files were upnpc.c and upnpcommands.c from the github project at https://github.com/miniupnp/miniupnp/tree/master/miniupnpc.

There's now a ttl parameter before `&error` that should be set to 2. — Matthew D. Scholefield, Jun 07 '20 at 20:51

how to use libminiupnpc to setup port forwarding

1 Answers1