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，但我的客户端无法recv（）或显示数据。任何人都可以帮我解决这个问题，或者可以提出一个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>
#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)
{
long etid; /*each thread id */
etid = (long)threadid;
pthread_t tid;
tid = pthread_self();
int sockfd;
struct sockaddr_in serv_addr;
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;
serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
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;
}
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"
void *connection_handler(void *);
int main(int argc , char *argv[])
{
int sockfd , new_socket , c , *new_sock;
struct sockaddr_in server , client;
char *message;
//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：0)
有几个问题：
在您的服务器中，您执行以下操作：
new_sock = malloc(1);
您只需分配1个字节来保存int空间不足。由于newsock指向int，因此您应为其中一个分配足够的空间：
new_sock = malloc(sizeof(int));
同样在服务器中，您在从客户端阅读消息后执行此操作：
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);
buff是未初始化的void *，因此尝试写入会导致未定义的行为。 write正从未初始化的buff在套接字上发送一个字节，这可能不是您想要的。然后通过套接字从message发送数据，而不将任何内容放入其中。
此处您真正需要做的就是直接从文件中读取message，然后send。您首先要清除message中的内存，以便在您从文件中读取后，它将以NULL结尾。
所以你可以用以下内容替换上面的内容：
fd = open (PROCESSLIST, O_RDONLY);
puts("file open has taken place");
memset(message, 0, sizeof(message));
read(fd, message, sizeof(message));
puts("reading the file");
//Send the message back to client
send(sock,message,strlen(message),0);
在客户端中，您有5个线程尝试同时读取用户的消息。只有其中一个能够。由于服务器忽略了客户端发送的数据，因此最好让每个客户端线程在不提示用户的情况下发送一些虚拟数据，然后在从服务器获取消息后退出。