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17.1 Connecting to a Remote Target

On the No value for GDBN host machine, you will need an unstripped copy of your program, since No value for GDBN needs symbol and debugging information. Start up No value for GDBN as usual, using the name of the local copy of your program as the first argument.

No value for GDBN can communicate with the target over a serial line, or over an IP network using TCP or UDP. In each case, No value for GDBN uses the same protocol for debugging your program; only the medium carrying the debugging packets varies. The target remote command establishes a connection to the target. Its arguments indicate which medium to use:

target remote serial-device

Use serial-device to communicate with the target. For example, to use a serial line connected to the device named ‘/dev/ttyb’:

target remote /dev/ttyb

If you're using a serial line, you may want to give No value for GDBN the ‘--baud’ option, or use the set remotebaud command (see section set remotebaud) before the target command.

target remote host:port
target remote tcp:host:port

Debug using a TCP connection to port on host. The host may be either a host name or a numeric IP address; port must be a decimal number. The host could be the target machine itself, if it is directly connected to the net, or it might be a terminal server which in turn has a serial line to the target.

For example, to connect to port 2828 on a terminal server named manyfarms:

target remote manyfarms:2828

If your remote target is actually running on the same machine as your debugger session (e.g. a simulator for your target running on the same host), you can omit the hostname. For example, to connect to port 1234 on your local machine:

target remote :1234

Note that the colon is still required here.

target remote udp:host:port

Debug using UDP packets to port on host. For example, to connect to UDP port 2828 on a terminal server named manyfarms:

target remote udp:manyfarms:2828

When using a UDP connection for remote debugging, you should keep in mind that the `U' stands for “Unreliable”. UDP can silently drop packets on busy or unreliable networks, which will cause havoc with your debugging session.

target remote | command

Run command in the background and communicate with it using a pipe. The command is a shell command, to be parsed and expanded by the system's command shell, /bin/sh; it should expect remote protocol packets on its standard input, and send replies on its standard output. You could use this to run a stand-alone simulator that speaks the remote debugging protocol, to make net connections using programs like ssh, or for other similar tricks.

If command closes its standard output (perhaps by exiting), No value for GDBN will try to send it a SIGTERM signal. (If the program has already exited, this will have no effect.)

Once the connection has been established, you can use all the usual commands to examine and change data and to step and continue the remote program.

Whenever No value for GDBN is waiting for the remote program, if you type the interrupt character (often Ctrl-c), No value for GDBN attempts to stop the program. This may or may not succeed, depending in part on the hardware and the serial drivers the remote system uses. If you type the interrupt character once again, No value for GDBN displays this prompt:

Interrupted while waiting for the program.
Give up (and stop debugging it)?  (y or n)

If you type y, No value for GDBN abandons the remote debugging session. (If you decide you want to try again later, you can use ‘target remote’ again to connect once more.) If you type n, No value for GDBN goes back to waiting.


When you have finished debugging the remote program, you can use the detach command to release it from No value for GDBN control. Detaching from the target normally resumes its execution, but the results will depend on your particular remote stub. After the detach command, No value for GDBN is free to connect to another target.


The disconnect command behaves like detach, except that the target is generally not resumed. It will wait for No value for GDBN (this instance or another one) to connect and continue debugging. After the disconnect command, No value for GDBN is again free to connect to another target.

monitor cmd

This command allows you to send arbitrary commands directly to the remote monitor. Since No value for GDBN doesn't care about the commands it sends like this, this command is the way to extend No value for GDBN—you can add new commands that only the external monitor will understand and implement.

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