我尝试使用以下代码实现多线程tcp服务器。
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 );
//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);
while( (client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c)) )
{
puts("Connection accepted");
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 newsockfd = *(int*)socket_desc;
int read_size;
char *message , buffer[2000];
int n;
struct auth details;
char* reply;
char cmd[100] = {0};
//Receive a message from client
while( (read_size = recv(newsockfd , buffer , 2000 , 0)) > 0 )
{
printf("Incoming data: %s", buffer);
if(parseData(cmd, buffer, "/", "-")) /* If received data is compliant */
{
details = authenticate(cmd);
if (details.verified) // If said user can execute this command.
{
reply = execute(cmd); // Execute.
n = write(newsockfd, reply, strlen(reply));
if (n < 0) { error("ERROR writing to socket"); }
free(reply);
reply = NULL;
}
else // Authentication failed.
{
n = write(newsockfd, details.error_msg, strlen(details.error_msg));
if (n < 0) { error("ERROR writing to socket"); }
else{
if(debug) printf("sent: %s\n", details.error_msg);
}
}
}
}
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
//Free the socket pointer
free(socket_desc);
return 0;
}
authenticate函数在实现文件中定义:
struct auth authenticate(const char* const command)
{
struct auth data;
char* db_pwd;
char* perm;
char* username = "testUser";
char query[200] = {0};
data.verified = FALSE;
data.error_msg = "";
printf("in auth\n");
MYSQL_ROW row;
snprintf(query, 200, "SELECT password FROM userlist WHERE user='%s'", username);
if ((row = mysql_fetch_row(run_query(query)))) // if user is on list
{
db_pwd = row[0];
if(!strcmp(db_pwd, password))
{
if (!(strcmp(command, "test")))
{
data.verified = TRUE;
}
}
}
return data;
}
我有一个工作单线程版本的这个程序(main)和相同的实现文件,只有多线程版本才会出现分段错误。
任何想法都会受到赞赏。
答案 0 :(得分:1)
阅读MySQL C API的文档,特别是§ 23.8.12 C API Threaded Function Descriptions它在内部使用与mysqld
服务器进程的套接字连接,因此您必须序列化所有MySQL函数。
因此,定义您的全局互斥锁,并使用该互斥锁保护所有执行mysql调用的函数(从请求获取回复的所有行)。更好的是,设计你的应用程序,以便只有一个单独的线程(通常是主线程)使用mysql函数。
编译所有警告和调试信息(gcc -Wall -g
)。使用调试器(gdb
)和valgrind
如果您不熟悉mutexes,则可能需要阅读pthread tutorial