udp_copy2 consists of two executables, udp_send2 and udp_recv2, implementing plain text non-interactive data transfer over UDP/IPv4 with a preset transfer rate. On lossy links, it yields better throughput than TCP-based transfers. It may also be used for smooth user space throttling. It dedicates a mode to SNAT/MASQ so the receiver can initiate transfer from behind a firewall. It features a very precise user space packet scheduler. It handles SIGSTOP in a rational way. It only transfers in one direction for one invocation. It needs and uses no synchronous I/O multiplexing. Shell access is required on both ends. The package also contains the auxiliary multi-threaded tool "bigpipe", which can be used to reduce pipeline latency.
udpeq balances UDP traffic over parallel routes, useful if you want to connect two endpoints through several slow or unreliable channels. For example, if you have three modem lines and a one-way satellite link, you might want to bond all of these together to form a faster, more reliable "virtual" connection.
uevalrun is a self-contained computation sandbox for Linux, using User-mode Linux for both compilation and execution of the program to be sandboxed. The program can be written in C, C++, Python, Ruby, Perl, or PHP. uevanrun enforces memory limits, timeouts, and output size limits in the sandbox. The primary use case for uevalrun is evaluation of solution programs submitted by contestants of programming contests: uevalrun compiles the solution, runs it with the test input, compares its output against the expected output, and writes a status report.
uhat is a tool that listens to joystick events and converts hat switch axis events into the joystick button events X-Plane needs. Some joysticks have hat switches that are represented to the OS as two axes, even though mechanically they're just four 0/1 switches. These hat switches are often used for looking around through the cockpit in X-Plane.
ui is a user information utility that can display user information, list users from a given UID (or UID 500 by default), add a user to a group, rename a user along with his home directory and update his home directory files to reflect that change, list expired or locked users, change the shell for a user, and list users in an existing group.