recvts

Section: WIN SYSTEM (1W)
Updated: 2000.8.14
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NAME

recvts - Receiving win format data from HDLC board

SYNOPSIS

recvts shmkey shmsize [ chfile [ logfile ]]

DESCRIPTION

Recvts receives win format data of satellite system delivery system 6Mbps line to be entered in the HDLC board (manufactured by Hakusan Corporation) for RS-422 interface of PC, and writes (cyclically) in the shared memory segment given by a key shmkey. When the shared memory segment having the key does not exist, shared memory segment of size shmsize (KB) is created. When the segment already exists but has a size smaller than shmsize (KB), an error will occur. The UDP port number is a 16-bit integer value, and shared memory key is a 32-bit integer value. When a channel file chfile is given, only channel data listed in the file is received. However, when '-' is attached to the head of the channel file name, data of all channels other than those listed in the file are received. When chfile is not specified or '-' is attached, all channels are received.

When log file name logfile is specified, operation log is set here. When it is not specified, log information is sent to the standard output. Log file is opened/closed in each write. Operation log contains statistics concerning data amount. This is written in log at the time of initiation and in each time when recvts receives the HUP signal, and the contents are packet number (np), byte (nb) and length of measuring period (per) after the previous time of write. Although data that recvts accepts from the HDLC line is packet of type 'A1,' amount of data measured as statistical information includes all data parts of the HDLC frame of all packet types. Therefore, net utilization ratio of line can be estimated from this information.
In case of the delivery system of satellite system in our university, packet size is about 3.7KB in average. Overhead due to flag etc. attached to the front and back of the HDLC frame may be less than 1% in case of large packet size like this level. In addition, in HDLC, when five "1s" format a row, extra one "0" is always inserted. Increase by this insertion also corresponds to 1% or less stochastically.

Recvts does not accept data packet at the time more than +/-30 minutes apart from internal clock of its own host. Therefore, as for host in which recvts is run, it is necessary to put clock right in a certain level.

Generally speaking, data received by recvts are not always sent in order of time of records. In this case, data are not arranged in order of time even on the shared memory in which recvts wrote. order(1W) permutes these data in order of time.

When recvts is initiated without argument, brief usage is displayed.

FORMAT ON HDLC

Data are transmitted by the HDLC packet, and has extended format of delivery system line. Recvts accepts only packet of packet type 'A1.'

RESENDING PROTOCOL

RS-422 line of delivery system allows one-way traffic and has no retransmission function.

Format on shared memory

See recvt(1W) for data format in which recvts writes the shared memory.

OPTIONS

None.

SOURCE

`recvts.c'

ACTION ENVIRONMENT

recvts is operated on FreeBSD and opens HDLC device /dev/brhdlc0 to read data from here.