我正在尝试从服务器端的文件/ tmp / k读取数据并将数据复制到消息并发送到客户端。在这里，我能够将数据发送到客户端并在客户端上显示。但是当我在客户端和服务器中添加头字段时，客户端显示核心转储。任何人都可以帮我解决问题，或者可以提出更好的解决方案来在客户端显示数据
由于
client.c
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/syscall.h>
#include <netdb.h>
#define MAX_SIZE 100000
#define NUM_CLIENT 5
void *connection_handler(void *);
int main(int argc , char *argv[])
{
int sockfd;
long i;
pthread_t sniffer_thread;
printf("memory allocated for the creation of socket \n");
for (i=1; i<=NUM_CLIENT; i++) {
if( pthread_create( &sniffer_thread , NULL , connection_handler , (void *) i) < 0)
{
perror("could not create thread");
return 1;
}
printf("Thread created \n");
sleep(2);
}
pthread_exit(NULL);
return 0;
}
void *connection_handler(void *threadid)
{
struct head
{
float version;
int msg_length;
int header_length;
char msg_type[50];
};
long etid; /*each thread id */
etid = (long)threadid;
pthread_t tid;
tid = pthread_self();
int sockfd , n;
struct sockaddr_in serv_addr;
struct hostent *server;
void *buf;
buf=(struct head *)malloc((sizeof(struct head)));
char sbuff[MAX_SIZE] , rbuff[MAX_SIZE];
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
printf("Failed creating socket\n");
perror("could not create thread");
return 0;
}
memset(&serv_addr, 0 , sizeof (serv_addr));
printf("the bytes of memory area pointed by serv_addr is filled with constant '0' \n");
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr,
(char *)&serv_addr.sin_addr.s_addr,
server->h_length);
serv_addr.sin_port = htons(8888);
if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof (serv_addr)) < 0) {
perror("Failed to connect to server. Error");
return 0;
}
n = read(sockfd,buf,((sizeof(struct head))));
printf("The socket contains %d \n ",n);
if (n < 0)
perror("ERROR reading from socket");
printf("version -->%f \n msg length -->%d \n header length %d \n msg type--> %s \n ",*(float*)buf,*(int*)((unsigned int)buf+sizeof(float)),*(int*)((unsigned int)buf+sizeof(float)+sizeof(int)),(char*)((unsigned int)buf+sizeof(float)+3*sizeof(int)));
printf("Connected successfully client:%ld \n", tid);
printf("before calling pthread_create getpid: %d getpthread_self: %lu tid:%lu\n",getpid(), pthread_self(), syscall(SYS_gettid));
while(1)
{
printf("For thread : %ld\n", etid);
printf("thread id given by kernel: %ld\n", tid);
fgets(sbuff, MAX_SIZE , stdin);
send(sockfd,sbuff,strlen(sbuff),0);
if(recv(sockfd,rbuff,MAX_SIZE,0)==0)
printf("Error");
else
fputs(rbuff,stdout);
bzero(rbuff,MAX_SIZE);
sleep(2);
}
close(sockfd);
return 0;
}
server.c
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/syscall.h>
#include<pthread.h> //for threading , link with lpthread
#include <fcntl.h>
#define PROCESSLIST "/tmp/k"
struct head
{
float version;
int msg_length;
int header_length;
char msg_type[50];
};
void *connection_handler(void *);
int main(int argc , char *argv[])
{
int sockfd , new_socket , c , *new_sock;
struct sockaddr_in serv_addr , client;
char *message;
void *msgptr;
struct head * hdptr;
int n;
hdptr=(struct head *)malloc(sizeof(struct head));
msgptr=malloc((sizeof(struct head)));
printf("msgptr1 %u size = %d\n",(unsigned int) msgptr,sizeof(struct head));
((struct head *)msgptr)->version=5.01;
((struct head *)msgptr)->msg_length=1234;
((struct head *)msgptr)->header_length=2;
strcpy((((struct head *)msgptr)->msg_type),"process list, directory list, OS Name and Version");
((struct head *)msgptr)->flag=0;
printf("intialized \n");
printf("version -->%f \n msg length -->%d \n header length %d \n msg type--> %s \n ",*((float *)msgptr),*((int *)((unsigned int)msgptr+sizeof(float))),*((int *)((unsigned int)msgptr+2*sizeof(int))),(char *)((unsigned int)msgptr+3*sizeof(int)));
//Create socket
sockfd = socket(AF_INET , SOCK_STREAM , 0);
if (sockfd == -1)
{
printf("Could not create socket");
}
//Prepare the sockaddr_in structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( 8888 );
//Bind
if( bind(sockfd,(struct sockaddr *)&server , sizeof(server)) < 0)
{
puts("bind failed");
return 1;
}
puts("bind done");
//Listen
listen(sockfd , 3);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
while( (new_socket = accept(sockfd, (struct sockaddr *)&client, (socklen_t*)&c)) )
{
puts("Connection accepted");
pthread_t sniffer_thread;
new_sock = malloc(1);
*new_sock = new_socket;
if( pthread_create( &sniffer_thread , NULL , connection_handler , (void*) new_sock) < 0)
{
perror("could not create thread");
return 1;
}
puts("Handler assigned");
}
if (new_socket<0)
{
perror("accept failed");
return 1;
}
return 0;
}
/* This will handle connection for each client */
void *connection_handler(void *sockfd)
{
//Get the socket descriptor
int sock = *(int*)sockfd;
int read_size;
char message[100000], client_message[2000];
int fd;
void *buff;
//Receive a message from client
while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
{
system ("ps -ef > /tmp/k");
puts("temp file getting created");
fd = open (PROCESSLIST, O_RDONLY);
puts("file open has taken place");
read(fd, buff, sizeof(*buff));
puts("reading the file");
write(sock, buff, 1);
puts("writing to the buffer");
puts("copied data from buffer to message");
//Send the message back to client
send(sock,message,strlen(message),0);
puts("data has been sent");
}
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
//Free the socket pointer
free(sockfd);
return 0;
}
答案 0 :(得分：1)
主要问题是你在未初始化的指针上使用了间接。
此
struct hostent *server;
几乎紧接着
bcopy(server->whatever
/* ^ this is wrong, because `server' is not initialized */
很难看到你的混乱（对不起，我的意思是代码）。您需要更好地组织代码。并检查错误以使其健壮。
以下是您的代码略有改进，我也解决了问题
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/syscall.h>
#include <netdb.h>
#define MAX_SIZE 100000
#define NUM_CLIENT 5
void *connection_handler(void *);
int main(int argc , char *argv[])
{
long i;
pthread_t sniffer_thread;
printf("memory allocated for the creation of socket \n");
for (i = 1 ; i <= NUM_CLIENT ; i++) /* Be consistent, either break braces or don't */
{
if (pthread_create(&sniffer_thread , NULL, connection_handler, (void *) &i) < 0)
{
perror("could not create thread");
return 1;
}
printf("Thread created \n");
sleep(2);
}
pthread_exit(NULL);
return 0;
}
void *connection_handler(void *threadid)
{
struct head
{
float version;
int msg_length;
int header_length;
char msg_type[50];
};
long etid; /*each thread id */
pthread_t tid;
int sockfd;
int n;
struct sockaddr_in serv_addr;
struct hostent server;
/* ^ you don't need a pointer */
void *buf;
char sbuff[MAX_SIZE];
char rbuff[MAX_SIZE];
tid = pthread_self();
etid = *(long *) threadid;
buf = malloc((sizeof(struct head)));
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("Failed creating socket\n");
perror("could not create thread");
return 0;
}
memset(&serv_addr, 0 , sizeof (serv_addr));
printf("the bytes of memory area pointed by serv_addr is filled with constant '0' \n");
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(8888);
bcopy((char *) server.h_addr, (char *) &serv_addr.sin_addr.s_addr, server.h_length);
if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof (serv_addr)) < 0)
{
perror("Failed to connect to server. Error");
return 0;
}
n = read(sockfd,buf,((sizeof(struct head))));
printf("The socket contains %d \n ",n);
if (n < 0)
perror("ERROR reading from socket");
printf(
"version -->%f \n msg length -->%d \n header length %d \n msg type--> %s \n ",
*(float *) buf,
*(int *) ((unsigned int *) buf + sizeof(float)),
*(int *) ((unsigned int *) buf + sizeof(float) + sizeof(int)),
(char *) ((unsigned int *) buf + sizeof(float) + 3 * sizeof(int))
/* ^ you need to cast to a pointer type */
);
printf("Connected successfully client:%ld \n", tid);
printf("before calling pthread_create getpid: %d getpthread_self: %lu tid:%lu\n",
getpid(), pthread_self(), syscall(SYS_gettid));
while (1)
{
printf("For thread : %ld\n", etid);
printf("thread id given by kernel: %ld\n", tid);
fgets(sbuff, MAX_SIZE , stdin);
send(sockfd,sbuff,strlen(sbuff),0);
if(recv(sockfd,rbuff,MAX_SIZE,0)==0)
printf("Error");
else
fputs(rbuff,stdout);
bzero(rbuff,MAX_SIZE);
sleep(2);
}
close(sockfd);
return 0;
}
server变量被指定为指针，但是当你取消引用它时它还没有指向任何东西。
由于未取消初始化，因此在取消引用时行为未定义。另外，在投射指针时你应该小心，这不是微不足道的，你已经犯过这样的错误
*(int *) ((unsigned int) buf + sizeof(float) + sizeof(int))
您正在将buf转换为整数，并且转换可能会截断指针，例如在x86_64平台上。启用编译器警告后，编译器会警告指向整数转换的指针。