con

A lightweight console utility for serial devices, TCP sockets, and UNIX domain sockets. A minimal minicom replacement with zero UI overhead. For serial and TCP usage modes, see the original README.

This document covers source build and installation, installed-path UDS verification, and UDS client features used for EPICS IOC console access via procServ.

Build and Install

Install the source acquisition, build, and UDS verification prerequisites for the target system.

Debian GNU/Linux 13

sudo apt-get update
sudo apt-get install --yes build-essential coreutils git util-linux

Rocky Linux 8.10

sudo dnf install --assumeyes gcc-c++ make coreutils git util-linux

From the released source root, build and install the binaries:

make
sudo make install DESTDIR=/usr/local
/usr/local/bin/con -V

Installed UDS Round Trip

Build the shipped AF_UNIX echo server and run the UDS integration test against the installed binary. This is the default installed-path check on Debian GNU/Linux 13 and Rocky Linux 8.10.

make -C tests/helpers clean all
CON_BIN=/usr/local/bin/con ECHO_SERVER_MODE=echo_server bash tests/test-uds-echo.bash

A successful run exits zero and reports Echo server returned test string as passed. The test creates and removes its temporary socket and stops the shipped echo server.

UDS Client Connection

Connect to a procServ IOC console:

con -c /run/procserv/myioc/control

Use -u or --unix to select UNIX transport explicitly. This also handles a colonless socket name that flagless mode would treat as a serial target and a name such as cache:6379 that would otherwise match the TCP host:port form:

Warning: server mode removes an existing target path before binding. Use a socket path that does not already exist.

con -u -c control.sock
con -u -c cache:6379
con --unix -s listen:6380

The option changes only the transport to UNIX. -c and -s still select client and server direction, and behavior without -u remains unchanged.

Quiet mode suppresses connection banners:

con -c /run/procserv/myioc/control -q

Detach with Ctrl-A (default exit key).

Read-only Monitoring

Observe an IOC console without sending any keyboard input. Prevents accidental command injection when multiple operators share a console:

con -r -c /run/procserv/myioc/control

Ctrl-A exits. The exit key is always active in read-only mode.

Diagnostic Hotkey (Ctrl-T)

Press Ctrl-T during an active session to pause incoming data and display receive buffer utilization:

[diag] con recv buffer: 49152 / 212992 bytes (23%) - NORMAL
[diag] paused -- press any key to resume

Press any key to resume. Buffer status levels:

Level	Threshold	Action
NORMAL	< 50%	No action required
HIGH	50-80%	Check remote for output flood, consider con -r
		If EPICS IOC, check for device driver errors or crash-loop
CRITICAL	> 80%	Remote output may block, disconnect or reduce output rate
		If EPICS IOC, restart IOC or check procServ crash-loop

When logging is active (-l or -a), diagnostic output is also written to the log file.

Custom Exit Key

The default exit key is Ctrl-A (0x01). To change it to Ctrl-B:

con -x ctrl/b -c /run/procserv/myioc/control

The -x argument accepts ctrl/a, cntrl/a, control-a forms, or raw integer values (0x02, 002).

Accepted formats: ctrl/a, cntrl/a, control-a, or raw integer (0x02, 002).

Logging

Overwrite mode:

con -c /run/procserv/myioc/control -l session.log

Append mode with timestamped session header:

con -c /run/procserv/myioc/control -a session.log

Strip ANSI escape sequences from log output (for color-enabled EPICS shells):

con -c /run/procserv/myioc/control -n -l clean.log

Hex Output Modes

Hex bytes:

con -X -c /run/procserv/myioc/control

Hex + ASCII (non-printable shown as .):

con -Y -c /run/procserv/myioc/control

Switch Reference

Switch	Description
-V, --version	Print version, git hash, and build date
-h	Print help message
-c	Connect as UDS or TCP client
-u, --unix	Force UNIX socket transport without changing client/server direction
-r	Read-only mode
-q	Suppress connection banners
-l FILE	Log to file (overwrite)
-a FILE	Append to log file with session header
-n	Strip ANSI escape sequences from log
-X	Hex byte output
-Y	Hex + ASCII output
-x KEY	Custom exit key (default: Ctrl-A)
-e	Echo keyboard input locally
Ctrl-T	Diagnostic: pause and display buffer status
Ctrl-A	Exit session (default, configurable with -x)

Testing

make test

The Ctrl-T diagnostic hotkey is covered by make test (tests/test-uds-diag.bash). The interactive test below is for flood mode and visual inspection of the [diag] output:

bash tests/manual-test-diag-hotkey.bash          # echo mode
bash tests/manual-test-diag-hotkey.bash --flood   # flood mode

Test specifications: tests/README.md and tests/TEST_DETAILS.md.

Cross-compilation Example (BLM)

/srv/librablmOpt is the NFS folder where the BLM can access as PATH.

source ../deviceconf/BLM/setEnvBLMCC.bash
make clean
make
sudo make install DESTDIR=/srv/liberablmOpt