2008-9-17 15:33

写一个程序想要接受网络上的UDP数据包，可是多数的数据包却蒸发掉了.
  s5 f0 M- o1 I" V8 C简化源码:9 Q, ^1 R$ P/ _0 D# r
    int sock;
  N- Q- u) K! v1 O& ]$ q" b* h& I& h7 S    struct sockaddr_in addr;6 ?9 N& n' j( i! j& O9 Y
    socklen_t len;' y" W/ B2 Q& Y5 S0 f8 Z6 i
    char buf[4096];0 y- P1 d0 |  m8 _8 e  K/ u
    size_t size;& K9 c; O% U/ o. p

9 X" ^- J( i3 o# j" k+ Y: R) V    sock = Socket(PF_INET,SOCK_DGRAM,0);0 L5 p! J6 H! k# n: Z0 @
    bzero(&addr,sizeof(addr));+ J2 c* N1 M" `# a
    addr.sin_family = AF_INET;; |) Q. x, y! W. |
    addr.sin_port = htons(2425);
8 R  j0 @+ a: b    addr.sin_addr.s_addr = htonl(INADDR_ANY);
$ ^8 ], u* c7 P% y3 z. [' E    bind(sock,(SA*)&addr,sizeof(addr))
2 Q3 U9 J7 Y1 Q2 U    while (1) {+ R7 R6 r& a+ q( k9 v
        len = sizeof(addr);1 r" U% G) V8 M0 f  h- G
        size = recvfrom(sock,buf,4096,0,&addr,&len);
! {' w4 @  ]6 f  y: Q$ b        buf[size] = '\0';
, V$ ?1 r& I; \& Z        printf(buf);
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程序 tcpdump (tcpdump -i eth0 -A 'udp and port 2425') 能够抓取到数据包,如下:3 m* Q: f$ N! W
20:46:27.155650 IP 192.168.1.103.fjitsuappmgr > 192.168.1.115.35325: UDP, length 500 {. E9 z3 o0 a- T1 r% s
[email=E..N....@......g...s]E..N....@......g...s[/email]    y...:._1:1221252224:OwnerENOVO-29C59B44:6291459:Owner.! J) V8 j' s: H- k, N6 f
可是我的程序却什么也得不到., c. b, d/ z5 t4 C& r
愿各位高手不吝赐教!
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[ 本帖最后由 jallyx 于 2008-9-16 15:30 编辑 ]　　　　　　

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引用:

-(dearvoid@:Forum)-(~/void/c/network)-8 M8 e9 X4 I: A1 b
[$$=3891 $?=0] ; cat udp_1.c( r5 F0 v+ j' z- A$ q8 N
#include " e5 M" a& Q0 ^4 x& x/ _' @- i& e
#include + x6 V9 {4 H: s: }, U% i- n6 }
#include
) \2 i4 n  H& Y; l$ ~& F9 H#include 7 l! s2 K) {# @
#include
, e/ v3 v# C4 Q6 A0 a#include
$ H8 t" u# d2 d! R% R) j#include
2 M; H2 B# x6 S8 I0 o#include
( K5 k6 b+ @! o! _' j#include   @) O5 _) _- X; r8 r* ^, K* g; }5 C
#include 2 `( O( F2 t& a; O6 x7 ?5 M
#include
/ z  T8 \9 p) q' Q3 G' x4 @/ t2 P#include
& {9 I3 b- B& d+ u! q. M' q4 a6 q
; e+ v+ u' l7 x, Sconst int g_serverPort = 20001;9 U! T1 @( l3 d3 n/ j, ^
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int/ d0 m3 C% N# v/ t# _. m
main()2 K0 H8 T/ H, B: |0 w. a+ X! A) h
{
5 ^5 Z/ [! r+ Y1 G/ A, f8 @    int sockServer, len;
# z4 p4 n' p+ y& G/ A    char buf[1024];
4 r* M) i% s7 t; u+ K- @' h7 Y    struct sockaddr_in saServer, saPeer;
. F; G3 u" _6 x& x4 g/ \, D- b    socklen_t socklen;
8 d3 c% R7 g+ [$ T$ _5 T9 R* |5 X+ X8 X; Q5 X
    sockServer = socket(AF_INET, SOCK_DGRAM, 0);- H1 s; @1 ]) _) x
    if (sockServer < 0) {- t3 i8 d$ ]4 Q" e1 D
        perror("socket");
& Y4 o4 b, [+ @$ q) c        exit(1);
2 b* a! Z) [: W3 R" C    }
# A. r$ e. E, H; M0 ^, i- J- |' S: e! t# `  ^4 F
    memset(&saServer, 0, sizeof saServer);5 B# G" u: c% C4 Y  |# [2 j/ |1 ~
    saServer.sin_family = AF_INET;/ g  V) ?5 y5 Q( D  P/ c9 x  `& b
    saServer.sin_addr.s_addr = INADDR_ANY;
6 v- N$ _* I6 C& O2 E    saServer.sin_port = htons(g_serverPort);8 @( \5 f! n: F9 Z# H
    if (bind(sockServer, (void *)&saServer, sizeof saServer) < 0) {, M2 Y; C8 K" W% g: w) N
        perror("bind");
6 [1 E! m9 v' q, T* z& z        exit(1);
' l: I' H) \* b$ S& `    }
  I; l5 `& N# I9 P4 b: g0 o4 `* [7 h% T' Y% c8 o! R- U0 z
    /*' N0 Q5 S' w- l4 v. f8 d% F
     * don't forget to init `socklen' !
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    socklen = sizeof saPeer;) g& r, j  z" K0 {
    len = recvfrom(sockServer, buf, sizeof buf, 0,
  s5 _2 v5 t% c                   (void *)&saPeer, &socklen);
' }) |3 ]1 L6 b" a4 R3 ?  B$ z    if (len < 0) {
3 }2 t# D7 Q! @" W( k# x1 J        perror("recvfrom");
0 F$ I  L' d( x$ f. @" x9 T6 r        exit(1);' [2 @4 d) j; I4 N1 E
    }- C" S, `! W/ E  h9 l
    if (len) {) `+ l, W5 o, R. D- {
        buf[len] = 0;7 u6 l" X6 l! m' z, V
        printf(">>> Received %d bytes from %s:%d\n", len,% ~/ S( |: |: h+ o) D
               inet_ntoa(saPeer.sin_addr), ntohs(saPeer.sin_port));
, L9 t# T0 C; ^        printf("%s\n", buf);
2 H8 d- Q: T0 y4 H- k    }
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% I, I0 Q8 g, Z# W    close(sockServer);
( \" J: `& c- e4 h
- [; Y# \' S1 v' W2 T! N    return 0;
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-(dearvoid@:Forum)-(~/void/c/network)-
7 a: ~- M5 R! o9 x5 x5 ]# i [$$=3891 $?=0] ; gcc udp_1.c5 W9 U: {0 a+ F, [% Y% C; `; D
-(dearvoid@:Forum)-(~/void/c/network)-
/ r- J' T$ A9 X: Q) |! M" u [$$=3891 $?=0] ; { sleep 10; echo -n 'hello, world' > /dev/udp/localhost/20001; } && N' |' F4 ~) H
[1] 5295
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[$$=3891 $?=0] ; ./a.out
. r5 z. A- _* K/ ~2 c* Y4 o+ K. y>>> Received 12 bytes from 127.0.0.1:327681 l; k* g/ Y0 i) q( F
hello, world
8 A' z" M' l7 x" s# J% h$ ~' D- ][1]+  Done                    { sleep 10; echo -n 'hello, world' > /dev/udp/localhost/20001; }
' h6 z2 C# d5 f" R. S-(dearvoid@:Forum)-(~/void/c/network)-* @4 j3 c+ K: U4 R2 |1 Z( w9 [
[$$=3891 $?=0] ; bye# p% L) z7 I: |4 }8 T

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