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Transferring a file with ipfs

This document is a guide to help troubleshoot transferring a file between two machines using ipfs.

A file transfer

To start, make sure that ipfs is running on both machines. To verify, run ipfs id on each machine and check if the Addresses field has anything in it. If it says null, then your node is not online and you will need to run ipfs daemon.

Now, lets call the node with the file you want to transfer node 'A' and the node you want to get the file to node 'B'. On node A, add the file to ipfs using the ipfs add command. This will print out the multihash of the content you added. Now, on node B, you can fetch the content using ipfs get <hash>.

# On A
> ipfs add myfile.txt
added QmZJ1xT1T9KYkHhgRhbv8D7mYrbemaXwYUkg7CeHdrk1Ye myfile.txt

# On B
> ipfs get QmZJ1xT1T9KYkHhgRhbv8D7mYrbemaXwYUkg7CeHdrk1Ye
Saving file(s) to QmZJ1xT1T9KYkHhgRhbv8D7mYrbemaXwYUkg7CeHdrk1Ye
 13 B / 13 B [=====================================================] 100.00% 1s

If that worked, and downloaded the file, then congratulations! You just used ipfs to move files across the internet! But, if that ipfs get command is hanging, with no output, read onwards.

Troubleshooting

So your ipfs file transfer appears to not be working. The primary reason this happens is because node B cannot figure out how to connect to node A, or node B doesn't even know it has to connect to node A.

Checking for existing connections

The first thing to do is to double check that both nodes are in fact running and online. To do this, run ipfs id on each machine. If both nodes show some addresses (like the example below), then your nodes are online.

{
        "ID": "QmTNwsFkLAed15kQEC1ZJWPfoNbBQnMFojfJKQ9sZj1dk8",
        "PublicKey": "CAASpgIwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDZb6znj3LQZKP1+X81exf+vbnqNCMtHjZ5RKTCm7Fytnfe+AI1fhs9YbZdkgFkM1HLxmIOLQj2bMXPIGxUM+EnewN8tWurx4B3+lR/LWNwNYcCFL+jF2ltc6SE6BC8kMLEZd4zidOLPZ8lIRpd0x3qmsjhGefuRwrKeKlR4tQ3C76ziOms47uLdiVVkl5LyJ5+mn4rXOjNKt/oy2O4m1St7X7/yNt8qQgYsPfe/hCOywxCEIHEkqmil+vn7bu4RpAtsUzCcBDoLUIWuU3i6qfytD05hP8Clo+at+l//ctjMxylf3IQ5qyP+yfvazk+WHcsB0tWueEmiU5P2nfUUIR3AgMBAAE=",
        "Addresses": [
                "/ip4/127.0.0.1/tcp/4001/ipfs/QmTNwsFkLAed15kQEC1ZJWPfoNbBQnMFojfJKQ9sZj1dk8",
                "/ip4/192.168.2.131/tcp/4001/ipfs/QmTNwsFkLAed15kQEC1ZJWPfoNbBQnMFojfJKQ9sZj1dk8",
        ],
        "AgentVersion": "go-ipfs/0.4.11-dev/",
        "ProtocolVersion": "ipfs/0.1.0"
}

Next, check to see if the nodes have a connection to each other. You can do this by running ipfs swarm peers on one node, and checking for the other nodes peer ID in the output. If the two nodes are connected, and the ipfs get command is still hanging, then something unexpected is going on, and I recommend filing an issue about it. If they are not connected, then let's try and debug why. (Note: you can skip to 'Manually connecting node A to node B' if you just want things to work. Going through the debugging process and reporting what happened to the ipfs team on IRC is helpful to us to understand common pitfalls that people run into)

Checking providers

When requesting content on ipfs, nodes search the DHT for 'provider records' to see who has what content. Let's manually do that on node B to make sure that node B is able to determine that node A has the data. Run ipfs dht findprovs <hash>. We expect to see the peer ID of node A printed out. If this command returns nothing (or returns IDs that are not node A), then no record of A having the data exists on the network. This can happen if the data is added while node A does not have a daemon running. If this happens, you can run ipfs dht provide <hash> on node A to announce to the network that you have that hash. Then if you restart the ipfs get command, node B should now be able to tell that node A has the content it wants. If node A's peer ID showed up in the initial findprovs call, or manually providing the hash didn't resolve the problem, then it's likely that node B is unable to make a connection to node A.

Checking addresses

In the case where node B simply cannot form a connection to node A, despite knowing that it needs to, the likely culprit is a bad NAT. When node B learns that it needs to connect to node A, it checks the DHT for addresses for node A, and then starts trying to connect to them. We can check those addresses by running ipfs dht findpeer <node A peerID> on node B. This command should return a list of addresses for node A. If it doesn't return any addresses, then you should try running the manual providing command from the previous steps. Example output of addresses might look something like this:

/ip4/127.0.0.1/tcp/4001
/ip4/192.168.2.133/tcp/4001
/ip4/88.157.217.196/tcp/63674

In this case, we can see a localhost (127.0.0.1) address, a LAN address (the 192.168.. one) and another address. If this third address matches your external IP, then the network knows a valid external address for your node. At this point, its safe to assume that your node has a difficult to traverse NAT situation. If this is the case, you can try to enable UPnP or NAT-PMP on the router of node A and retry the process. Otherwise, you can try manually connecting node A to node B.

Manually connecting node A to B

On node B run ipfs id and take one of the multiaddrs that contains its public ip address, and then on node A run ipfs swarm connect <multiaddr>. You can also try using a relayed connection, for more information read this doc. If that still doesn't work, then you should either join IRC and ask for help there, or file an issue on github.

If this manual step did work, then you likely have an issue with NAT traversal, and ipfs cannot figure out how to make it through. Please report situations like this to us so we can work on fixing them.

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