C语言 接受来自客户端的数据时的 Seg 错误

Question

我正在尝试设置服务器并发回HTTP响应对我来说很困难，我的代码是seg错误，我不知道为什么。

这是我的代码供参考

我知道这是一个内存问题，但我不知道在哪里，它会打印到 while 循环中的接受行。

#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), bind(), and connect() */
#include <arpa/inet.h> /* for sockaddr_in and inet_ntoa() */
#include <stdlib.h> /* for atoi() and exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
//#include <sys/types.h>
#include <netdb.h>
//#include <sys/stat.h>
#define MAXPENDING 5 /* Maximum outstanding connection requests */
#define RCVBUFSIZE 2048
#define CONTENTLENGTH 20,000
void DieWithError(char *errorMessage); /* Error handling function */
void DieWithError (char *errorMessage)
{
printf(errorMessage);
printf("n");
}
//void HandleTCPClient(int clntSocket); /* TCP client handling function */
int main(int argc, char *argv[])
{
//while loop over everything
// listen for client connect
// bind the socket
// accept the client Socket
// read from socket/ parse the command
// send an appt repsonse header and body
// close socket
// free memory
// ctrl c thing where u clear all memory before terminating (optional)
struct sockaddr_in clientData;
struct sockaddr_in servData;
int cSock, sSock, binder, listener, acceptor, receivedData, sentData;
unsigned int cAddr;
unsigned short sAddr;
char res[1024];
char *root;
if (argc != 2)
{
printf("Usage : nt ./server portNumbern");
exit(1);
}
sAddr = atoi(argv[1]);
sSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (sSock < 0)
{
DieWithError("serv socket failed");
}
memset(&servData, 0 , sizeof(servData));
servData.sin_family = AF_INET;
servData.sin_addr.s_addr = htonl(INADDR_ANY);
servData.sin_port = htons(sAddr);
memset(&clientData, 0, sizeof(char));
binder = bind(sSock, (struct sockaddr *) &servData, sizeof (servData));
listener = listen(sSock, MAXPENDING);
if (listener < 0)
{
DieWithError("listen did not work");
exit(1);
}
while (1)
{
char buffer[RCVBUFSIZE];// = (char*) malloc(RCVBUFSIZE * sizeof(char));
printf("oddden");
//cAddr = sizeof(clientData);
cSock = accept (sSock, (struct sockaddr *) &clientData, sizeof(clientData.sin_addr));
printf("Client %sn", inet_ntoa(clientData.sin_addr));
//cSock = accept (sSock, (struct sockaddr *) &clientData, &cAddr);
printf("oke mann");
receivedData = recv(cSock, buffer, RCVBUFSIZE-1, 0);
buffer[RCVBUFSIZE] = '';
if (receivedData < 0)
{
DieWithError("recv failure");
}
char *ip = (char*) malloc(strlen(argv[1]) * sizeof(char));
char *file, *port, *temp;
temp = argv[1];
//port = argv[2];
file = "/";
if (file = strstr(temp, "/"))
{
ip = strndup(temp, file - temp);
}
else
{
ip = strdup(temp);
}
if (strcmp(file, "/index.html") == 0)
{
printf("HTTP/1.1 200 OK rn");
fprintf("Content-Length: %s rn",CONTENTLENGTH);
printf("rn");
}
else
{
printf("HTTP/1.1 404 NOT FOUND rn");
fprintf("Content Length: %s rn", CONTENTLENGTH);
printf("rn");
}
sentData = send(cSock, buffer, receivedData, 0);
if (sentData < 0)
{
DieWithError("sending data failure");
}

}
close (cSock);
free(receivedData);
return 0;
}

输出：

Segmentation fault : 11
recv() failed

代码应该发回正确的 http 响应消息， 我有一个 client.c 用于测试此代码，如果我删除套接字行(用于测试(，它似乎不会退出 while 循环，主要问题是我不了解来源的分段错误。这是我的网络入门课的作业，明天到期。

Answer 1

发布的代码会导致编译器 (gcc( 输出几个警告：

我如何编译发布的代码：其中"untitled.c"是我为您发布的代码的本地名称。

gcc    -ggdb -Wall -Wextra -Wconversion -pedantic -std=gnu11  -c "untitled.c"  

现在，编译器的输出列表：

untitled.c: In function ‘DieWithError’:
untitled.c:18:6: warning: format not a string literal and no format arguments [-Wformat-security]
printf(errorMessage);
^~~~~~
untitled.c: In function ‘main’:
untitled.c:48:14: warning: conversion to ‘short unsigned int’ from ‘int’ may alter its value [-Wconversion]
sAddr = atoi(argv[1]);
^~~~
untitled.c:78:67: warning: passing argument 3 of ‘accept’ makes pointer from integer without a cast [-Wint-conversion]
cSock = accept (sSock, (struct sockaddr *) &clientData, sizeof(clientData.sin_addr));
^~~~~~
In file included from untitled.c:2:0:
/usr/include/x86_64-linux-gnu/sys/socket.h:232:12: note: expected ‘socklen_t * restrict {aka unsigned int * restrict}’ but argument is of type ‘long unsigned int’
extern int accept (int __fd, __SOCKADDR_ARG __addr,
^~~~~~
untitled.c:82:26: warning: conversion to ‘int’ from ‘ssize_t {aka long int}’ may alter its value [-Wconversion]
receivedData = recv(cSock, buffer, RCVBUFSIZE-1, 0);
^~~~
untitled.c:95:15: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
if (file = strstr(temp, "/"))
^~~~
untitled.c:97:35: warning: conversion to ‘size_t {aka long unsigned int}’ from ‘long int’ may change the sign of the result [-Wsign-conversion]
ip = strndup(temp, file - temp);
^~~~
untitled.c:107:24: warning: passing argument 1 of ‘fprintf’ from incompatible pointer type [-Wincompatible-pointer-types]
fprintf("Content-Length: %s rn",CONTENTLENGTH);
^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from untitled.c:1:0:
/usr/include/stdio.h:312:12: note: expected ‘FILE * restrict {aka struct _IO_FILE * restrict}’ but argument is of type ‘char *’
extern int fprintf (FILE *__restrict __stream,
^~~~~~~
untitled.c:13:23: warning: passing argument 2 of ‘fprintf’ makes pointer from integer without a cast [-Wint-conversion]
#define CONTENTLENGTH 20,000
^
untitled.c:107:50: note: in expansion of macro ‘CONTENTLENGTH’
fprintf("Content-Length: %s rn",CONTENTLENGTH);
^~~~~~~~~~~~~
In file included from untitled.c:1:0:
/usr/include/stdio.h:312:12: note: expected ‘const char * restrict’ but argument is of type ‘int’
extern int fprintf (FILE *__restrict __stream,
^~~~~~~
untitled.c:113:24: warning: passing argument 1 of ‘fprintf’ from incompatible pointer type [-Wincompatible-pointer-types]
fprintf("Content Length: %s rn", CONTENTLENGTH);
^~~~~~~~~~~~~~~~~~~~~~~~~
In file included from untitled.c:1:0:
/usr/include/stdio.h:312:12: note: expected ‘FILE * restrict {aka struct _IO_FILE * restrict}’ but argument is of type ‘char *’
extern int fprintf (FILE *__restrict __stream,
^~~~~~~
untitled.c:13:23: warning: passing argument 2 of ‘fprintf’ makes pointer from integer without a cast [-Wint-conversion]
#define CONTENTLENGTH 20,000
^
untitled.c:113:51: note: in expansion of macro ‘CONTENTLENGTH’
fprintf("Content Length: %s rn", CONTENTLENGTH);
^~~~~~~~~~~~~

In file included from untitled.c:1:0:
/usr/include/stdio.h:312:12: note: expected ‘const char * restrict’ but argument is of type ‘int’
extern int fprintf (FILE *__restrict __stream,
^~~~~~~
untitled.c:117:42: warning: conversion to ‘size_t {aka long unsigned int}’ from ‘int’ may change the sign of the result [-Wsign-conversion]
sentData = send(cSock, buffer, receivedData, 0);
^~~~~~~~~~~~
untitled.c:117:22: warning: conversion to ‘int’ from ‘ssize_t {aka long int}’ may alter its value [-Wconversion]
sentData = send(cSock, buffer, receivedData, 0);
^~~~
untitled.c:91:24: warning: unused variable ‘port’ [-Wunused-variable]
char *file, *port, *temp;
^~~~
untitled.c:90:17: warning: variable ‘ip’ set but not used [-Wunused-but-set-variable]
char *ip = (char*) malloc(strlen(argv[1]) * sizeof(char));
^~
untitled.c:127:11: warning: passing argument 1 of ‘free’ makes pointer from integer without a cast [-Wint-conversion]
free(receivedData);
^~~~~~~~~~~~
In file included from untitled.c:4:0:
/usr/include/stdlib.h:563:13: note: expected ‘void *’ but argument is of type ‘int’
extern void free (void *__ptr) __THROW;
^~~~

untitled.c:41:12: warning: unused variable ‘root’ [-Wunused-variable]
char *root;
^~~~
untitled.c:40:11: warning: unused variable ‘res’ [-Wunused-variable]
char res[1024];
^~~
untitled.c:38:19: warning: unused variable ‘cAddr’ [-Wunused-variable]
unsigned int cAddr;
^~~~~
untitled.c:37:42: warning: unused variable ‘acceptor’ [-Wunused-variable]
int cSock, sSock, binder, listener, acceptor, receivedData, sentData;
^~~~~~~~
untitled.c:37:24: warning: variable ‘binder’ set but not used [-Wunused-but-set-variable]
int cSock, sSock, binder, listener, acceptor, receivedData, sentData;
^~~~~~

在这些警告中，有一条消息是关于对函数使用错误的语法：fprintf()

以及关于"int"和char*之间转换的几个警告

这些类型的警告至关重要。

然后有很多关于未使用的变量和设置但从未使用的变量的警告。

关于：#define CONTENTLENGTH 20,000逗号"，"不能作为数字内的分隔符。 编译器会将其视为 20 和一些杂散值 000

在启用警告的情况下进行编译，然后修复这些警告

强烈建议您阅读/理解您正在使用的每个 C 库函数的 MAN 页。