# Copyright (c) 2017 - 2019 LiteSpeed Technologies Inc.  See LICENSE.
LSQUIC Examples
===============

test/http_client.c demonstrates how to use HTTP features of QUIC.

Usage Examples
--------------

Fetch Google's home page:

    ./http_client -s www.google.com -p /

The default port number is 443, but it can be specified after colon
using the -s flag.  The value of the `host' header as well as the SNI
value defaults to the host part of the -s option.  -H option can be
used to override it.  For example:

    ./http_client -H www.youtube.com -s www.google.com:443 -p / -M HEAD

The host part can be an IP address.  Both IPv4 and IPv6 are supported.
See ./http_client -h for a (long) list of different flags.

POST a file to calculate its CRC32 checksum:

    ./http_client -H www.litespeedtech.com -s 443 \
                        -p /cgi-bin/crc32.cgi -P file-256M -M POST

    HTTP/1.1 200 OK
    content-type: text/plain
    date: Fri, 09 Jun 2017 08:40:45 GMT
    server: LiteSpeed
    alt-svc: quic=":443"; v="35,37"

    CRC32: 2A0E7DBB

This is a good way to check that the payload gets to the other side
correctly.  The CGI script is:

    #!/usr/bin/perl
    use String::CRC32;
    printf "Content-type: text/plain\r\n\r\nCRC32: %X\n", crc32(*STDIN)

On the command line, I do

    alias crc32="perl -MString::CRC32 -e'printf qq(%X\n), crc32(<>)'"

To submit several requests concurrently, one can use -n and -r options:

    ./http_client -H www.litespeedtech.com -s 443 \
                -p /cgi-bin/crc32.cgi -P file-256M -M POST -n 3 -r 10

This will open three parallel connections which will make ten POST
requests together.

To perform load testing, it is good to mix sending and receiving data:

    for i in {1..100}; do
        ./http_client $COMMON_OPTS -p /cgi-bin/crc32.cgi -P file-256M \
                                                    -M POST >out-post.$i &
        ./http_client $COMMON_OPTS -p /docs/file-256M >out-get.$i        &
        sleep 1
    done

If you don't want to create a hundred 256-megabyte out-get.* files, use -K
flag to discard output.

Control QUIC Settings via -o Flag
---------------------------------

Most of the settings in struct lsquic_engine_settings can be controlled
via -o flag.  With exception of es_versions, which is a bit mask, other
es_* options can be mapped to corresponding -o value via s/^es_//:

    es_cfcw             =>  -o cwcf=12345
    es_max_streams_in   =>  -o max_streams_in=123

And so on.

The code to set options via -o flag lives in set_engine_option().  It is good
to update this function at the same time as member fields are added to struct
lsquic_engine_settings.

Control LSQUIC Behavior via Environment Variables
-------------------------------------------------

LSQUIC_PACER_INTERTICK

    Number of microsecods to use as constant intertick time in lieu of the
    pacer's dynamic intertick time approximation.

    Only available in debug builds.

LSQUIC_CUBIC_SAMPLING_RATE

    Number of microseconds between times CWND is logged at info level.

    Only available in debug builds.

LSQUIC_RANDOM_SEND_FAILURE

    Frequency with which sending of packets fails: one out of this many
    times on average.

    Only available when compiled with -DLSQUIC_RANDOM_SEND_FAILURE=1

Control Network-Related Stuff
-----------------------------

   -D          Set `do not fragment' flag on outgoing UDP packets.

   -z BYTES    Maximum size of outgoing UDP packets.  The default is 1370
               bytes for IPv4 socket and 1350 bytes for IPv6 socket.

   -S opt=val  Socket options.  Supported options:
                   sndbuf=12345    # Sets SO_SNDBUF
                   rcvbuf=12345    # Sets SO_RCVBUF

More Compilation Options
------------------------

-DFULL_CONN_STATS=1

    Track some statistics about full connection -- packets in, sent, delayed,
    stream payload per packet size ratio, and some others -- and print them
    at NOTICE level when connection is destroyed.

    This is useful when performing network testing and especially analyzing
    the effects of changing send buffer size (see -S sndbuf= in the previous
    section).

-DLSQUIC_PACKINTS_SANITY_CHECK=1

    Turn on sanity checking for packet interval code.  The packet interval
    code, shared by both send and receive history modules, contained a bug
    which prompted me to add a checking function.

-DLSQUIC_SEND_STATS=0

    Turn off statistics collection performed by the send controller: number
    of packets sent, resent, and delayed.

-DLSQUIC_LOWEST_LOG_LEVEL=LSQ_LOG_WARN

    If you want to go even faster: compile out some log levels entirely.

-DLSQUIC_EXTRA_CHECKS=1

    Add relatively expensive run-time sanity checks

-DLSQUIC_RANDOM_SEND_FAILURE=1

    Simulate failure to send packets to test send resumption logic.  When
    this flag is specified, sending of packets will randomly fail, about
    one out of every 10 attempts.  Set environment variable
    LSQUIC_RANDOM_SEND_FAILURE to change this frequency.