From owner-freebsd-net@freebsd.org Tue Mar 5 22:46:19 2019 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A557E15199F6 for ; Tue, 5 Mar 2019 22:46:19 +0000 (UTC) (envelope-from meka@tilda.center) Received: from mail.tilda.center (srv02.tilda.center [199.247.21.11]) by mx1.freebsd.org (Postfix) with ESMTP id 402A18C66F for ; Tue, 5 Mar 2019 22:46:18 +0000 (UTC) (envelope-from meka@tilda.center) Received: from hal9000.home.meka.rs (178-223-64-96.dynamic.isp.telekom.rs [178.223.64.96]) by mail.tilda.center (Postfix) with ESMTPSA id 40E6317C83 for ; Tue, 5 Mar 2019 23:46:10 +0100 (CET) Date: Tue, 5 Mar 2019 23:46:10 +0100 From: Goran =?utf-8?B?TWVracSH?= To: freebsd-net@freebsd.org Subject: UDP broadcast Message-ID: <20190305224610.frw5ov5bn6f3xaqg@hal9000.home.meka.rs> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="2a3j36kn3vh2ku6h" Content-Disposition: inline User-Agent: NeoMutt/20180716 X-Rspamd-Queue-Id: 402A18C66F X-Spamd-Bar: -------- Authentication-Results: mx1.freebsd.org; spf=pass (mx1.freebsd.org: domain of meka@tilda.center designates 199.247.21.11 as permitted sender) smtp.mailfrom=meka@tilda.center X-Spamd-Result: default: False [-8.03 / 15.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; R_SPF_ALLOW(-0.20)[+mx]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.20)[multipart/signed,text/plain]; TO_DN_NONE(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-net@freebsd.org]; RCPT_COUNT_ONE(0.00)[1]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; DMARC_NA(0.00)[tilda.center]; MX_GOOD(-0.01)[mail.tilda.center]; NEURAL_HAM_SHORT(-0.99)[-0.995,0]; SIGNED_PGP(-2.00)[]; RCVD_NO_TLS_LAST(0.10)[]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+,1:+]; ASN(0.00)[asn:20473, ipnet:199.247.16.0/21, country:US]; RCVD_COUNT_TWO(0.00)[2]; IP_SCORE(-2.72)[ip: (-9.49), ipnet: 199.247.16.0/21(-4.59), asn: 20473(0.54), country: US(-0.07)]; RECEIVED_SPAMHAUS_PBL(0.00)[96.64.223.178.zen.spamhaus.org : 127.0.0.11] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Mar 2019 22:46:20 -0000 --2a3j36kn3vh2ku6h Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Hello, I have a audio mixer which is controleable over network via android app. The discovery is done by sending broadcast UDP message "/info\0\0\0" to 255.255.255.255 (checked by tcpdump on the router). I thought I can do the same with: printf "/info\0\0\0" | nc -4u -w 0 255.255.255.255 10024 But I never get the reply. This is what tcpdump sees: tcpdump -nnSX -v 'src 192.168.5.80 or dst 255.255.255.255' tcpdump: listening on re0, link-type EN10MB (Ethernet), capture size 262144 bytes 23:41:25.595663 IP (tos 0x0, ttl 64, id 28810, offset 0, flags [none], proto UDP (17), length 36, bad cksum 0 (->4439)!) 192.168.5.94.36465 > 255.255.255.255.10024: UDP, length 8 0x0000: 4500 0024 708a 0000 4011 0000 c0a8 055e E..$p...@......^ 0x0010: f fff ffff 8e71 2728 0010 c627 2f69 6e66 .....q'(...'/inf 0x0020: 6f00 0000 o... I never get any reply, but when I try the same with the android app while sniffing on the router: tcpdump -nnSX -v -i bridge0 'dst 255.255.255.255 or src 192.168.5.80' tcpdump: listening on bridge0, link-type EN10MB (Ethernet), capture size 262144 bytes 23:43:52.165821 IP (tos 0x0, ttl 64, id 20743, offset 0, flags [DF], proto UDP (17), length 36) 192.168.5.79.57477 > 255.255.255.255.10024: UDP, length 8 0x0000: 4500 0024 5107 4000 4011 23cb c0a8 054f E..$Q.@.@.#....O 0x0010: ffff ffff e085 2728 0010 2559 2f69 6e66 ......'(..%Y/inf 0x0020: 6f00 0000 o... 23:43:52.171565 IP (tos 0x0, ttl 128, id 8, offset 0, flags [none], proto UDP (17), length 84) 192.168.5.80.10024 > 192.168.5.79.57477: UDP, length 56 0x0000: 4500 0054 0008 0000 8011 aea1 c0a8 0550 E..T...........P 0x0010: c0a8 054f 2728 e085 0040 2677 2f69 6e66 ...O'(...@&w/inf 0x0020: 6f00 0000 2c73 7373 7300 0000 5630 2e30 o...,ssss...V0.0 0x0030: 3400 0000 5852 3138 2d32 372d 3031 2d34 4...XR18-27-01-4 0x0040: 3700 0000 5852 3138 0000 0000 312e 3039 7...XR18....1.09 0x0050: 0000 0000 .... So what am I doing wrong and how can I send UDP broadcast from either script of C code? Thank you! 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