sendto - receive files from a web browser

I wrote this in a fit of pique after someone wanted to send me some large multi-gigabyte files and asked which service I wanted to use. "This is ridiculous," I thought. "Sending stuff from one computer to another is what the internet is for."

This is currently only tested on Ubuntu Linux 20.02.

Fastest way to use

1. Configure your router to forward port 80 to another port (called $PORT) on your computer. $PORT must be greater than 1024). Note your external address on the router (called $ADDR)
2. At an sh command line, run mkdir -p ~/sendto/files
3. Run sendto -dir ~/sendto/files/
4. Give the sender the url http\://$ADDR:$PORT/
5. The sender can now send you a file using that url!

More convenient, more secure setup

1. Configure your router to forward port 80 and port 443 to your computer. Note your external address on the router (called $ADDR). The ports on your computer must also be 80 and 443 for certbot to work.
2. At a sh command line, run mkdir -p ~/sendto/{files,certs}
3. Set up a DNS entry on a domain name you own, like sendto.example.com
4. Use certbot from https://letsencrypt.com/ to generate an SSL private key and public certificate for your domain and put it in the certs directory.

 sudo certbot certonly --standalone
 sudo chown $USER {privkey,cert}.pem
 mv {privkey,cert}.pem ~/sendto/certs

5. Under Linux, give the binary the low-port binding capability:

sudo setcap cap_net_bind_service=+ep ~/go/bin/sendto

6. Run sendto:

sendto -dir ~/sendto/files/ \
 -key ~/sendto/certs/privkey.pem \
 -cert ~/sendto/certs/cert.pem \
 -hostname sendto.example.com

7. The sender can now send you a file using https\://sendto.example.com/!

Argument reference

• -dir : (required) Path to output directory. sendto must have write access.
• -port : Port to use for insecure web connections. Defaults to 80.
• -sport : Port to use for secure web connections. Defaults to 443.
• -key : Path to private key for secure web connections.
• -cert : Path to SSL certificate for secure web connections.
• -hostname : External hostname. This is used only for a redirect when someone connects with an insecure http connection.

Build instructions

1. Download the sendto source tarball.
2. You should have the Go language installed, which you can get from [https://golang.com/].
3. Put the source where the Go build tools expect:

mkdir -p ~/go/src/
tar -C ~/go/src/ sendto.tgz

4. Build and install:

go install sendto

The sendto program should be at ~/go/bin/sendto