Swap Meet

For smooth file transfer between computers, companies typically use file servers or locally installed cloud instances. But server-based systems require a capable hardware infrastructure; they need to be managed by an administrator and can pose vulnerabilities if configured incorrectly. If you only need to exchange a few files between individual workstations from time to time, these solutions are usually oversized.

It is far easier and faster to send and receive data using applications installed locally on workstations that work on a peer-to-peer basis. You don't need a server, and the data only travels back and forth between the participating computers without being stored on a third system.

Requirements

When choosing a tool to transfer data directly between two computers, there are a few things you need to consider. Most importantly, the tool needs to secure the data with end-to-end encryption so that third parties cannot sniff the data.

Simple file transfer does not require complex graphical user interfaces (GUIs). All that is needed is a command-line application with a manageable command set that can be used without extensive configuration and lengthy training.

If file synchronization is important, some peer-to-peer solutions for data transfer can additionally keep files and folders permanently synchronized between the participating computers.

Finally, for administrators of heterogeneous IT infrastructures, cross-platform availability is also an important decision-making criterion. The tool needs to support the popular client operating systems, preferably with standardized operation across platforms.

In this article, I will cover a few peer-to-peer tools for file sharing on local networks. (See the "Not Considered" box for tools that didn't make the cut.)

croc

The free croc [1] command-line tool transfers one or more files between two computers without an intermediate instance, using a transparently set up relay on the LAN. Written in Go, the cross-platform application is available for countless variants of Linux, even for 32-bit hardware. In addition, croc can be used on ARM systems and on various BSD derivatives. Data exchange between all supported platforms is problem-free. Besides corresponding packages, the source code is available for download on croc's GitHub page.

Using croc

croc's end-to-end encryption follows the Password Authenticated Key Exchange (PAKE) standard [2], which uses a freely definable secure password to generate a key for file transfer on both computers involved. croc is the only tool in the test that can resume interrupted data transfers at a later time.

In the simplest case, the sender starts the transfer by entering

croc send FILE

It is important to specify the full path in each case, unless you are in the corresponding file directory.

The software then generates a code that the recipient needs to receive the data. The recipient then enters the code at the prompt by typing:

croc CODE

The program will then prompt the user to confirm the file to be sent. If confirmed, the transfer starts. croc visualizes this on both systems with a progress bar (Figure 1). It also shows the recipient's IP address and the port used. After completing the transfer process, the transferred file sits in the recipient's home directory.

Figure 1: No need for a GUI: croc handles file transfers from the command line.