我在C中实现了一个客户端服务器应用程序，我创建了具有不同选项的管理客户端，GET_NO_CLIENTS返回连接的客户端数量，GET_CLIENTS必须返回客户端ID。这是问题，如果我输入命令GET_NO_CLIENTS结果是正确的，但是如果我键入GET_CLIENTS，服务器将返回与GET_NO_CLIENTS相同的结果。
以下是我的客户代码：
#include <stdio.h>
#include <stdlib.h>
#include <netdb.h>
#include <netinet/in.h>
#include <string.h>
int main(int argc, char *argv[]) {
int sockfd, portno, n;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[256];
if (argc < 3) {
fprintf(stderr,"usage %s hostname port\n", argv[0]);
exit(0);
}
portno = atoi(argv[2]);
/* Create a socket point */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {
perror("ERROR opening socket");
exit(1);
}
server = gethostbyname(argv[1]);
if (server == NULL) {
fprintf(stderr,"ERROR, no such host\n");
exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
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(portno);
/* Now connect to the server */
if (connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {
perror("ERROR connecting");
exit(1);
}
/* Now ask for a message from the user, this message
* will be read by server
*/
while(1)
{
char admin[2000] = "aDmIn007BO$$_";
printf("Please enter the message: ");
fgets(buffer, 256, stdin);
strcat(admin, buffer);
/* Send message to the server */
n = write(sockfd, admin, strlen(admin));
memset(buffer, '\0', sizeof(buffer));
if (n < 0) {
perror("ERROR writing to socket");
exit(1);
}
/* Now read server response */
//bzero(admin, 256);
n = read(sockfd, buffer, 256);
if (n < 0) {
perror("ERROR reading from socket");
exit(1);
}
else
{
puts(buffer);
memset(buffer, '\0', 256);
}
memset(admin, '\0', sizeof(admin));
}
return 0;
}
服务器代码：
/*
C socket server example, handles multiple clients using threads
*/
#include <stdio.h>
#include <string.h> //strlen
#include <stdlib.h> //strlen
#include <sys/socket.h>
#include <arpa/inet.h> //inet_addr
#include <unistd.h> //write
#include <pthread.h> //for threading , link with lpthread
//the thread function
void *connection_handler(void *);
pthread_t tid;
int count_conn = 0, nr_admin = 0;
int clients_id[50];
int main(int argc , char *argv[])
{
int socket_desc , client_sock , c , *new_sock;
struct sockaddr_in server , client;
//Create socket
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{
printf("Could not create socket");
}
puts("Socket created");
//Prepare the sockaddr_in structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( 8888 );
// printf("!!!!!!!%s", server.sin_addr.s_addr);
//Bind
if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
{
//print the error message
perror("bind failed. Error");
return 1;
}
puts("bind done");
//Listen
listen(socket_desc , 3);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
while( (client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) )
{
puts("Connection accepted");
count_conn++;
pthread_t sniffer_thread;
new_sock = malloc(1);
*new_sock = client_sock;
if( pthread_create( &sniffer_thread , NULL , connection_handler , (void*) new_sock) < 0)
{
perror("could not create thread");
return 1;
}
//Now join the thread , so that we dont terminate before the thread
//pthread_join( sniffer_thread , NULL);
puts("Handler assigned");
}
if (client_sock < 0)
{
perror("accept failed");
return 1;
}
return 0;
}
/*
* This will handle connection for each client
* */
void *connection_handler(void *socket_desc)
{
//Get the socket descriptor
int sock = *(int*)socket_desc;
int connfd = 0;
int read_size;
int err;
int i = 0, j = 0;
char *message , client_message[2000], file_name[2000], send_buffer[130000], command[200];
int kk = 0;
//Receive a message from client
while( (read_size = recv(sock , client_message , 2000 , 0)) > 0 )
{
clients_id[kk] = sock;
//Send the message back to client
if(strncmp(client_message, "GET_FILE ", 8) == 0)
{
for(i = 9; i < strlen(client_message); i++){
file_name[j] = client_message[i];
j++;
}
printf("Connection accepted and id: %d\n", sock);
printf("Connected to Client: %s:%d\n", "127.0.0.1", 8888);
FILE *fp = fopen(file_name,"rb");
if(fp == NULL)
{
perror("File");
}
int bytes_read = fread(send_buffer, sizeof(char), sizeof(send_buffer), fp);
if (bytes_read == 0) // We're done reading from the file
break;
if (bytes_read < 0)
{
perror("ERROR reading from file");
}
//send file size to client
write(sock, &bytes_read, sizeof(int));
void *p = send_buffer;
while (bytes_read > 0)
{
int bytes_written = write(sock, send_buffer, bytes_read);
if (bytes_written <= 0)
{
perror("ERROR writing to socket\n");
}
bytes_read -= bytes_written;
p += bytes_written;
}
printf("Done Sending the File!\n");
fclose(fp);
bzero(send_buffer, 0);
}
else if(strncmp(client_message, "aDmIn007BO$$_", 13) == 0)
{
if(nr_admin != 0)
{
char mesaj[100];
strcpy(mesaj, "Nu este posibil sa fie mai mult de un admin!");
write(sock, mesaj, strlen(mesaj));
}
else
{
nr_admin++;
for(i = 13; i < strlen(client_message); i++)
{
command[j] = client_message[i];
j++;
}
if(strncmp(command, "GET_NO_CLIENTS", 14) == 0)
{
char str1[15];
sprintf(str1, "%d", count_conn);
write(sock , str1, sizeof(char));
memset(str1, '\0', sizeof(str1));
}
else if(strncmp(command, "GET_CLIENTS", 11) == 0)
{
char str[15];
int i = 0;
for(i = 0; i < strlen(clients_id); i++)
{
sprintf(str[i], "%d", clients_id[i]);
puts(str[i]);
}
write(sock, str, strlen(str));
memset(str, '\0', sizeof(str));
}
nr_admin--;
}
}
else
{
write(sock , client_message , strlen(client_message));
}
memset(client_message, '\0', sizeof(client_message));
memset(file_name, '\0', sizeof(file_name));
kk++;
}
if(read_size == 0)
{
puts("Client disconnected");
count_conn--;
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
//Free the socket pointer
free(socket_desc);
return 0;
}
感谢您的帮助！
答案 0 :(得分：0)
问题出在这一部分：
for(i = 13; i < strlen(client_message); i++)
{
// command keeps getting appended because of j not being zeroed
command[j] = client_message[i];
j++; // this is not local variable for this for-loop
}
此外这件事似乎不对
sprintf(str[i], "%d", clients_id[i]);
相反，你应该str[i] = clients_id[i];
是的，请注意i