---
name: "fromport"
section: "1"
platform: "linux"
package: "netstd"
version: "3.07-7slink.3"
release: "Debian 2.1 (Slink)"
platforms: ["linux"]
url: "https://new.carta.tech/fromport"
---

# fromport(1)

read data from a TCP/IP data stream toport - write data to a TCP/IP data stream

## NAME

fromport - read data from a TCP/IP data stream\
 toport - write data to a TCP/IP data stream

## SYNOPSIS

**fromport \[-v\] port**\
 **toport \[-b blocksize\] \[-p\] \[-t\] \[-v\] host port**

## DESCRIPTION

**Fromport** is a tiny little program that can be used to act as the "reader" end of a TCP/IP based network pipe between two processes.  It usually reads this data from a stream generated by the companion program called **toport** which does the reverse: it reads data from a program, device or file and sends it to a network connection.

The various options of these programs determine the way they can be used, but it will be clear that the probable use is that of a remote pipe between two copy processes, like with the commands:

```
hosta# tar cfv - * | toport hostB 30205
```

and

```
hostb# fromport 30205 | tar xfv -
```

on two TCP/IP connected hosts.  The **fromport** commandline on machine **hostb** creates a network connection that is listening to port number **30205** on that host, with the incoming data on that connection being sent to the **tar** program for further processing.  The **toport** commandline on machine **hosta** causes a **tar-style** archive to be created of the files and directories in and under the current directory, which is then sent onto the network connection to port **30205** on the **hostb** machine.

Alternatively, by selecting port **discard** (9) or **echo** (10) on the selected host, you can instruct the other side to either ignore our data, or to just echo it back.  This, combined with the **-t** option (see below) sets up a very raw TCP I/O perforance measurement tool.  A sample commandline would look like this:

```
hosta# cat /dev/dsk/hda1 | toport -t hostb 9
```

to test the performance to host **hostb** on the local network.

## OPTIONS

- **-b blocksize**

  Set the size of the I/O buffers used by the programs.  On most systems it pays off to use a larger buffer size than the default one of **1024** bytes.  For large data transfers, increasing this value to **8192** , **32768** or even **65536** can drastically reduce network and system load caused by the programs.

- **-n**

  Print the debugged values in IP **dotted-decimal** style, rather than the corresponding host names.

- **-t**

  Enable the printing of some transfer statistics.  This can be very useful for checking out the raw network TCP performance.

- **-v**

  Enter verbose mode, most useful for debugging things.

## BUGS

None so far.  What can you expect with a program this size?

## AUTHORS

Fred N. van Kempen, \<waltje@uwalt.nl.mugnet.org\>\
 Danny ter haar, \<dth@cistron.nl\>