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My single threaded HTTP Server works just fine, but I'm having trouble multithreading it. I know I am supposed to use pthreads, locks, and condition variables, but I can't get the logic set up properly. The trouble starts after listening to the server. Currently I have a struct that contains a client socket variable, a lock variable, a condition variable, and some variables necessary for parsing and storing headers. I create a struct array sized with the amount of threads, then create a pthread array sized with the amount of threads. I go into a while(1) loop which goes into a for loop and iterates through all the threads accepting each connection, calling pthread_create and passing them to my handle connections function, then closing the client socket. My handle connections then does the request handling that my single threaded http server did (reading, parsing, processing, constructing), then returns NULL. No request gets read when I run this using pthread_create, but if I run handle connections without the pthreads, it works just fine. And below I'll attach my code. Any help is appreciated
Thank you for commenting so well ...
Okay, I coded up, but not tested the changes.
Your loop is inherently single threaded, so a bit of refactoring is in order
You have to scan for an unused thread control slot after doing accept.
You have to pthread_join completed/done threads [from any prior invocations].
The thread function has to close the per-client socket [not main thread]
You need a global (file scope) mutex.
I've coded it up, but not tested it. I put #if 0 around most of what I clipped out and #if 1 around new code.
Note that number of simultaneous connections [second arg to listen], herein 5 has to be less than or equal to threadNum. Although I didn't do it, I'd just do listen(...,threadNum) instead of hardwiring it.
Here's the short code with just the relevant changes:
#if 1
pthread_mutex_t global_mutex = PTHREAD_MUTEX_INITIALIZER;
#endif
struct threadObject {
char method[5]; // PUT, HEAD, GET. HEAD==4 letters+null terminator
char filename[28]; // what is the file we are worried about. Max 27 ASCII characters (NULL terminated on 28)
char httpversion[9]; // HTTP/1.1
ssize_t content_length; // example: 13
uint16_t status_code; // status code for the request
char buffer[BUFFER_SIZE]; // buffer to transfer data
char rest_of_PUT[BUFFER_SIZE]; // incase client send part of PUT message in header
int client_sockd;
pthread_mutex_t *dispatch_lock;
const pthread_cond_t *job_pool_empty;
// pthread_mutex_t* log_lock;
// const pthread_cond_t* log_pool_empty;
pthread_mutex_t *read_write_lock;
pthread_cond_t *file_list_update;
// JobQueue* job_pool;
// LogQueue log_pool;
// bool is_logging;
#if 1
pthread_t tsk_threadid;
int tsk_inuse;
int tsk_done;
#endif
};
void *
handle_connections(void *ptr_thread)
{
// create a mutual exclusion to lock out any other threads from the function
// pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
// pthread_mutex_lock(&mutex);
// operations go here
struct threadObject *thread = (struct threadObject *) ptr_thread;
// reset message after each loop
memset(thread->buffer, '\0', BUFFER_SIZE);
memset(thread->method, '\0', 5);
memset(thread->filename, '\0', 28);
memset(thread->httpversion, '\0', 9);
thread->content_length = 0;
thread->status_code = 0;
memset(thread->rest_of_PUT, '\0', BUFFER_SIZE);
// read message
if (read_http_response(thread) == true) {
// process message
process_request(thread);
}
// construct a response
construct_http_response(thread);
// unlock the function
// pthread_mutex_unlock(&mutex);
#if 1
close(thread->client_sockd);
pthread_mutex_lock(&global_mutex);
thread->tsk_done = 1;
pthread_mutex_unlock(&global_mutex);
#endif
return NULL;
}
int
main(int argc, char **argv)
{
// Create sockaddr_in with server information
if (argc < 2) {
perror("No arguments passed\n");
return -1;
}
// make sure port number is above 1024 and set the port # to it
if (atoi(argv[1]) < 1024) {
return 1;
}
char *port = argv[1];
// parse the command line args for options -l and -N. -l specifies it will use a log and the following parameter is the filename. -N specifies the number of threads it will use and the following parameter will be a number
int opt;
uint8_t threadNum = 1;
char *logName = NULL;
while ((opt = getopt(argc - 1, argv + 1, "N:l:")) != -1) {
if (opt == 'N') {
threadNum = atoi(optarg);
}
else if (opt == 'l') {
logName = optarg;
}
}
struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(atoi(port));
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
socklen_t addrlen = sizeof(server_addr);
// Create server socket
int server_sockd = socket(AF_INET, SOCK_STREAM, 0);
// Need to check if server_sockd < 0, meaning an error
if (server_sockd < 0) {
perror("socket");
return 1;
}
// Configure server socket
int enable = 1;
// This allows you to avoid: 'Bind: Address Already in Use' error
int ret = setsockopt(server_sockd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable));
if (ret < 0) {
return EXIT_FAILURE;
}
// Bind server address to socket that is open
ret = bind(server_sockd, (struct sockaddr *) &server_addr, addrlen);
if (ret < 0) {
return EXIT_FAILURE;
}
// Listen for incoming connections
ret = listen(server_sockd, 5); // 5 should be enough, if not use SOMAXCONN
if (ret < 0) {
return EXIT_FAILURE;
}
struct threadObject thread[threadNum];
// Connecting with a client
struct sockaddr client_addr;
socklen_t client_addrlen = sizeof(client_addr);
// create a pthread array of size (number of threads). specify this will be using the handle connections function. join the threads together
#if 0
pthread_t thread_id[threadNum];
#endif
#if 1
struct threadObject *tsk = NULL;
int tskidx;
// clear out the thread structs
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
memset(tsk,0,sizeof(struct threadObject));
}
while (true) {
// accept connection
int client_sockd = accept(server_sockd, &client_addr, &client_addrlen);
pthread_mutex_lock(&global_mutex);
// join any previously completed threads
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
if (tsk->tsk_done) {
pthread_join(tsk->tsk_threadid,NULL);
tsk->tsk_inuse = 0;
tsk->tsk_done = 0;
}
}
// find unused task slot
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
if (! tsk->tsk_inuse)
break;
}
memset(tsk,0,sizeof(struct threadObject));
tsk->client_sockd = client_sockd;
tsk->tsk_inuse = 1;
pthread_mutex_unlock(&global_mutex);
// fire in the hole ...
pthread_create(&tsk->tsk_threadid, NULL, handle_connections, tsk);
}
#endif
#if 0
for (int i = 0; i < threadNum; i++) {
printf("\n[+] server is waiting...\n");
thread[i].client_sockd = accept(server_sockd, &client_addr, &client_addrlen);
handle_connections(&thread[i]);
// pthread_create(&thread_id[i], NULL, handle_connections, &thread[i]);
printf("Response Sent\n");
// close the current client socket
close(thread[i].client_sockd);
}
}
#endif
return EXIT_SUCCESS;
}
Here's the complete code [just in case I clipped out too much]:
#include <sys/socket.h>
#include <sys/stat.h>
#include <stdio.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <fcntl.h>
#include <unistd.h> // write
#include <string.h> // memset
#include <stdlib.h> // atoi
#include <stdbool.h> // true, false
#include <errno.h>
#include <sys/types.h>
#include <ctype.h>
#include <pthread.h>
#define BUFFER_SIZE 4096
#if 1
pthread_mutex_t global_mutex = PTHREAD_MUTEX_INITIALIZER;
#endif
struct threadObject {
char method[5]; // PUT, HEAD, GET. HEAD==4 letters+null terminator
char filename[28]; // what is the file we are worried about. Max 27 ASCII characters (NULL terminated on 28)
char httpversion[9]; // HTTP/1.1
ssize_t content_length; // example: 13
uint16_t status_code; // status code for the request
char buffer[BUFFER_SIZE]; // buffer to transfer data
char rest_of_PUT[BUFFER_SIZE]; // incase client send part of PUT message in header
int client_sockd;
pthread_mutex_t *dispatch_lock;
const pthread_cond_t *job_pool_empty;
// pthread_mutex_t* log_lock;
// const pthread_cond_t* log_pool_empty;
pthread_mutex_t *read_write_lock;
pthread_cond_t *file_list_update;
// JobQueue* job_pool;
// LogQueue log_pool;
// bool is_logging;
#if 1
pthread_t tsk_threadid;
int tsk_inuse;
int tsk_done;
#endif
};
//read in the header and store it in the appropriate places
bool
read_http_response(struct threadObject *thread)
{
printf("\nThis function will take care of reading message\n");
// how many bytes we're receiving from the header. also puts the message into the buffer
ssize_t bytes = recv(thread->client_sockd, thread->buffer, BUFFER_SIZE, 0);
// if nothing or too much gets sent in the header, return
if (bytes <= 0 || bytes >= BUFFER_SIZE) {
thread->status_code = 400;
printf("Too long or nothing in here\n");
return false;
}
// NULL terminate the last spot on the buffer
thread->buffer[bytes] = '\0';
// how many bytes we received
printf("[+] received %ld bytes from client\n[+] response: \n", bytes);
printf("those bytes are: %s\n", thread->buffer);
// make a char pointer pointer to the buffer to easily traverse it and parse it into the right spots
char *traverse = thread->buffer;
// first stop. sgnals the beginning of the filename
char *file = strstr(traverse, "/");
// 2nd stop. signls the beginning of the HTTP version. only 1.1 is accepted
char *http = strstr(traverse, "HTTP/1.1");
// 3rd stop. Signals the beginning of the content length
char *contlength1 = strstr(traverse, "Content-Length");
char *chunked = strstr(traverse, "chunked");
if (chunked != NULL) {
printf("MESSAGE NOT A FILE PUT\n");
thread->status_code = 403;
return false;
}
// store the method
sscanf(traverse, "%s", thread->method);
printf("method:%s\n", thread->method);
// if its not 1 of the 3 valid requests, throw 400 error
if (strcmp(thread->method, "GET") != 0 &&
strcmp(thread->method, "PUT") != 0 &&
strcmp(thread->method, "HEAD") != 0) {
thread->status_code = 400;
printf("Invalid Method:%s\n", thread->method);
return false;
}
// if the filename doesnt start with /, its invalid throw 400 error
if (*file != '/') {
thread->status_code = 400;
printf("bad filename\n");
return false;
}
// only store the filename portion after the required /
traverse = file + 1;
// to make sure the filename isnt too long
uint8_t size_check = 0;
// traverse filename until first whitespace
while (*traverse != ' ') {
// if any character in the filename isnt 1 of these, its invalid. throw 400 error
if (!isalnum(*traverse) && *traverse != '_' && *traverse != '-') {
// if theres no filename at all, throw a 404 error
if (size_check == 0) {
thread->status_code = 404;
printf("No file specified\n");
return thread->status_code;
}
thread->status_code = 400;
printf("Invalid filename character:%c\n", *traverse);
return false;
}
sscanf(traverse++, "%c", thread->filename + size_check++);
// if the filename breaks the 27 character limit, return a 400 error
if (size_check > 27) {
thread->status_code = 400;
printf("filename too long\n");
return false;
}
}
printf("filename:%s\n", thread->filename);
// if HTTP/1.1 isnt given, throw a 400 error
if (http == NULL) {
printf("HTTP/1.1 400 Bad Request\r\n\r\n");
thread->status_code = 400;
return false;
}
traverse = http;
// read in the http version until the first \r\n. this signals the end of the given version name
sscanf(traverse, "%[^\r\n]s", thread->httpversion);
printf("HTTP:%s\n", thread->httpversion);
// if its not a put request, this is the end of the header. return
if (strcmp(thread->method, "PUT") != 0) {
return true;
}
// for put requests only. traverse until the beginning of the content length
traverse = contlength1;
// last stop. signals the end of a normal PUT header. if a client wants to put some of the message in the header, it gets stored after this
char *end = strstr(traverse, "\r\n\r\n");
// if theres no \r\n\r\n, the header is bad. return 400
if (end == NULL) {
printf("bad header\n");
thread->status_code = 400;
return false;
}
// traverse to the next digit
while (!isdigit(*traverse)) {
// if theres no next digit after "content length", the header is bad. return 400
if (traverse == end) {
printf("bad header\n");
thread->status_code = 400;
return false;
}
traverse++;
}
// set to traverse to be sure fit the entire content length. use size_check to traverse through
char *temp = traverse;
size_check = 0;
// while its taking in digits, put them into the char array.
while (isdigit(*traverse)) {
sscanf(traverse++, "%c", temp + size_check++);
}
// convert the new string into numbers
thread->content_length = atoi(temp);
// if the content length is < 0 throw a 400 error
if (thread->content_length < 0) {
thread->status_code = 400;
printf("bad content length:%ld\n", thread->content_length);
return false;
}
// printf("Content Length:%ld\n", thread->content_length);
// move +4 spots to get to the end of this. if its a normal PUT, this will be the last spot. If the client puts part of the message in the header, it goes after this
traverse = end + 4;
// put the rest of the header into a char array to append later. if theres nothing, itll do nothing
strcpy(thread->rest_of_PUT, traverse);
// printf("Rest of PUT:%s\n", thread->rest_of_PUT);
// will only get here if status code is 0
return true;
}
//process the message we just recieved
void
process_request(struct threadObject *thread)
{
printf("\nProcessing Request\n");
// server side file descriptor
int fd;
// if the method is PUT
if (strcmp(thread->method, "PUT") == 0) {
// open the file for read only to check if its already there or not to set proper status code
fd = open(thread->filename, O_WRONLY);
// if it doesnt exist, set 201 status code
struct stat checkExist;
if (stat(thread->filename, &checkExist) != 0) {
thread->status_code = 201;
}
// if it exists, set 200 and overwrite
else {
struct stat fileStat;
fstat(fd, &fileStat);
// check write permission
if ((S_IWUSR & fileStat.st_mode) == 0) {
printf("MESSAGE NOT WRITEABLE PUT\n");
thread->status_code = 403;
return;
}
thread->status_code = 200;
}
// close it
close(fd);
// reopen it. this time for writing to or overwriting. if its there, overwrite it. if not, create it. cant use for status codes since it will always create a new file
fd = open(thread->filename, O_WRONLY | O_CREAT | O_TRUNC);
// printf("fd in process is:%d\n", fd);
// if theres a bad fd, throw a 403
if (fd < 0) {
printf("ERROR\n\n");
thread->status_code = 403;
return;
}
// to check that the amount of bytes sent = the amount received
ssize_t bytes_recv,
bytes_send;
// if theres no body, put an empty file on the server
if (thread->content_length == 0) {
bytes_send = write(fd, '\0', 0);
}
// if there is a body, put it onto the new file created on the server and make sure the received bytes = the sent ones
else {
ssize_t total = 0,
len_track = thread->content_length;
while (thread->content_length != 0) {
bytes_recv = recv(thread->client_sockd, thread->buffer, BUFFER_SIZE, 0);
bytes_send = write(fd, thread->buffer, bytes_recv);
total += bytes_send;
// if the received bytes != the sent byes, send a 500 error
if (bytes_recv != bytes_send) {
thread->status_code = 500;
printf("Recieved != sent for put request\n");
return;
}
thread->content_length -= bytes_recv;
// printf("Bytes read:%ld\nBytes sent:%ld\nMessage content length:%ld\n", bytes_recv, bytes_send, message->content_length);
}
// if the content length != bytes sent, throw a 403 error
if (len_track != total) {
thread->status_code = 403;
printf("Content length != sent for put request\n");
return;
}
}
printf("Message status code:%d\n", thread->status_code);
// close the fd
close(fd);
return;
}
// if the method is GET or HEAD
else if (strcmp(thread->method, "GET") == 0 || strcmp(thread->method, "HEAD") == 0) {
// open the file for reading only
fd = open(thread->filename, O_RDONLY);
// if bad fd, throw a 404
struct stat fileStat;
fstat(fd, &fileStat);
// check read permission and if it exists
if (((S_IRUSR & fileStat.st_mode) == 0) || stat(thread->filename, &fileStat) != 0) {
printf("BAD GET\n");
thread->status_code = 404;
return;
}
else {
thread->status_code = 200;
thread->content_length = lseek(fd, 0, SEEK_END);
}
// close the fd
close(fd);
return;
}
}
void
construct_http_response(struct threadObject *thread)
{
printf("Constructing Response\n");
// size 22 since the largest code is 21 characters + NULL
char response[22];
// 200=OK, 201=CREATED, 400=BAD REQUEST, 403=FORBIDDEN, 404=NOT FOUND, 500=INTERNAL SERVER ERROR
if (thread->status_code == 200) {
strcpy(response, "OK");
}
else if (thread->status_code == 201) {
strcpy(response, "CREATED");
}
else if (thread->status_code == 400) {
strcpy(response, "BAD REQUEST");
}
else if (thread->status_code == 403) {
strcpy(response, "FORBIDDEN");
}
else if (thread->status_code == 404) {
strcpy(response, "NOT FOUND");
}
else if (thread->status_code == 500) {
strcpy(response, "INTERNAL SERVER ERROR");
}
else {
printf("Bad response...\n");
return;
}
dprintf(thread->client_sockd, "%s %d %s\r\nContent-Length: %ld\r\n\r\n", thread->httpversion, thread->status_code, response, thread->content_length);
if (strcmp(thread->method, "GET") == 0 && thread->status_code == 200) {
int fd = open(thread->filename, O_RDONLY);
ssize_t total = 0,
len_track = thread->content_length,
bytes_recv,
bytes_send;
while (thread->content_length != 0) {
bytes_recv = read(fd, thread->buffer, BUFFER_SIZE);
bytes_send = send(thread->client_sockd, thread->buffer, bytes_recv, 0);
if (bytes_recv != bytes_send) {
thread->status_code = 500;
close(fd);
printf("Recieved != sent for GET request\nReceived:%ld\nSent:%ld\n", bytes_recv, bytes_send);
dprintf(thread->client_sockd, "%s %d %s\r\nContent-Length: %ld\r\n\r\n", thread->httpversion, thread->status_code, response, thread->content_length);
close(fd);
return;
}
total += bytes_send;
thread->content_length -= bytes_recv;
}
if (total != len_track) {
thread->status_code = 403;
printf("Content length != recvd for GET request\n");
dprintf(thread->client_sockd, "%s %d %s\r\nContent-Length: %ld\r\n\r\n", thread->httpversion, thread->status_code, response, thread->content_length);
close(fd);
return;
}
close(fd);
}
}
void *
handle_connections(void *ptr_thread)
{
// create a mutual exclusion to lock out any other threads from the function
// pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
// pthread_mutex_lock(&mutex);
// operations go here
struct threadObject *thread = (struct threadObject *) ptr_thread;
// reset message after each loop
memset(thread->buffer, '\0', BUFFER_SIZE);
memset(thread->method, '\0', 5);
memset(thread->filename, '\0', 28);
memset(thread->httpversion, '\0', 9);
thread->content_length = 0;
thread->status_code = 0;
memset(thread->rest_of_PUT, '\0', BUFFER_SIZE);
// read message
if (read_http_response(thread) == true) {
// process message
process_request(thread);
}
// construct a response
construct_http_response(thread);
// unlock the function
// pthread_mutex_unlock(&mutex);
#if 1
close(thread->client_sockd);
pthread_mutex_lock(&global_mutex);
thread->tsk_done = 1;
pthread_mutex_unlock(&global_mutex);
#endif
return NULL;
}
int
main(int argc, char **argv)
{
// Create sockaddr_in with server information
if (argc < 2) {
perror("No arguments passed\n");
return -1;
}
// make sure port number is above 1024 and set the port # to it
if (atoi(argv[1]) < 1024) {
return 1;
}
char *port = argv[1];
// parse the command line args for options -l and -N. -l specifies it will use a log and the following parameter is the filename. -N specifies the number of threads it will use and the following parameter will be a number
int opt;
uint8_t threadNum = 1;
char *logName = NULL;
while ((opt = getopt(argc - 1, argv + 1, "N:l:")) != -1) {
if (opt == 'N') {
threadNum = atoi(optarg);
}
else if (opt == 'l') {
logName = optarg;
}
}
struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(atoi(port));
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
socklen_t addrlen = sizeof(server_addr);
// Create server socket
int server_sockd = socket(AF_INET, SOCK_STREAM, 0);
// Need to check if server_sockd < 0, meaning an error
if (server_sockd < 0) {
perror("socket");
return 1;
}
// Configure server socket
int enable = 1;
// This allows you to avoid: 'Bind: Address Already in Use' error
int ret = setsockopt(server_sockd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable));
if (ret < 0) {
return EXIT_FAILURE;
}
// Bind server address to socket that is open
ret = bind(server_sockd, (struct sockaddr *) &server_addr, addrlen);
if (ret < 0) {
return EXIT_FAILURE;
}
// Listen for incoming connections
ret = listen(server_sockd, 5); // 5 should be enough, if not use SOMAXCONN
if (ret < 0) {
return EXIT_FAILURE;
}
struct threadObject thread[threadNum];
// Connecting with a client
struct sockaddr client_addr;
socklen_t client_addrlen = sizeof(client_addr);
// create a pthread array of size (number of threads). specify this will be using the handle connections function. join the threads together
#if 0
pthread_t thread_id[threadNum];
#endif
#if 1
struct threadObject *tsk = NULL;
int tskidx;
// clear out the thread structs
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
memset(tsk,0,sizeof(struct threadObject));
}
while (true) {
// accept connection
int client_sockd = accept(server_sockd, &client_addr, &client_addrlen);
pthread_mutex_lock(&global_mutex);
// join any previously completed threads
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
if (tsk->tsk_done) {
pthread_join(tsk->tsk_threadid,NULL);
tsk->tsk_inuse = 0;
tsk->tsk_done = 0;
}
}
// find unused task slot
for (tskidx = 0; tskidx < threadNum; tskidx++) {
tsk = &thread[tskidx];
if (! tsk->tsk_inuse)
break;
}
memset(tsk,0,sizeof(struct threadObject));
tsk->client_sockd = client_sockd;
tsk->tsk_inuse = 1;
pthread_mutex_unlock(&global_mutex);
// fire in the hole ...
pthread_create(&tsk->tsk_threadid, NULL, handle_connections, tsk);
}
#endif
#if 0
for (int i = 0; i < threadNum; i++) {
printf("\n[+] server is waiting...\n");
thread[i].client_sockd = accept(server_sockd, &client_addr, &client_addrlen);
handle_connections(&thread[i]);
// pthread_create(&thread_id[i], NULL, handle_connections, &thread[i]);
printf("Response Sent\n");
// close the current client socket
close(thread[i].client_sockd);
}
}
#endif
return EXIT_SUCCESS;
}
Fairly new to socket programming, so here goes my question. What is wrong? What my function does, is take input from the telnet session and then when you press 'enter' it should go break the while loop. But it doesn't for some reason. I can't figure out why either, I've tried various ways but, nothing I've tried thus far worked yet.
void handle_clients(socket,address)
int *socket;
const char *address;
{
char msg[256];
char cmd[128];
int bytes;
memset(msg,0,sizeof(msg));
memset(cmd,0,sizeof(cmd));
while(1) {
send(*socket,"CMD >> ",7,0);
bytes = 0;
while((bytes = recv(*socket,cmd,sizeof(cmd),0)) > 0) {
if(bytes < 0) {
sprintf(msg,"Error: receiving from %s.\r\n",
address);
send(*socket,msg,strlen(msg),0);
break;
}
if(cmd[bytes] == 10 || cmd[bytes] == 13) {
break;
}
}
if(strcmp(cmd,"exit") == 0) {
break;
} else if(strcmp(cmd,"help") == 0) {
sprintf(msg,"Commands: [exit,cmd,help]\r\n");
send(*socket,msg,strlen(msg),0);
} else if(strcmp(cmd,"cmd") == 0) {
memset(cmd,0,sizeof(cmd));
send(*socket,"Enter command: ",15,0);
bytes = 0;
while((bytes = recv(*socket,cmd,sizeof(cmd),0)) > 0) {
if(bytes < 0) {
sprintf(msg,"Error: receiving from %s.\r\n",
address);
send(*socket,msg,strlen(msg),0);
break;
}
if(cmd[bytes] == 10 || cmd[bytes] == 13) {
break;
}
}
system(cmd);
} else {
sprintf(msg,"Unknown command.\r\n");
send(*socket,msg,strlen(msg),0);
}
memset(msg,0,sizeof(msg));
memset(cmd,0,sizeof(cmd));
}
}
it should go break the while loop. But it doesn't for some reason.
In addition to the issues pointed out by my peers, I think the answer to your specific inquiry lies in the nested while loops and the missing \r\n chars from the strcmp.
Since the while loops are nested, than break might break the nested loop while the container loop remains - so you're back in the next nested loop in your next iteration.
For example:
while(1) {
send(*socket,"CMD >> ",7,0);
bytes = 0;
while((bytes = recv(*socket,cmd,sizeof(cmd),0))) {
if(bytes < 0) {
sprintf(msg,"Error: receiving from %s.\r\n",
address);
send(*socket,msg,strlen(msg),0);
break; /* <= WHICH LOOP ARE WE BREAKING? */
}
if(cmd[bytes] == 10 || cmd[bytes] == 13) {
break; /* <= WHICH LOOP ARE WE BREAKING? */
}
}
// ...
}
This is one of those cases where goto might be your friend...
...although I do think there are better and more elegant solutions and changes that might be required to your code before you go there.
Also, What's the point of re-reading the data, if you're overwriting the existing buffer?
I find it almost (in this case) more convenient and likely to ignore the possible case of incomplete TCP/IP packets/commands.
In this specific case, it seems okay to assume that if the command doesn't end with a new line, something is wrong and we can disconnect. Such short commands should pass in a single TCP/IP packet. i.e.:
while(1) {
send(*socket,"CMD >> ",7,0);
bytes = 0;
bytes = recv(*socket,cmd,sizeof(cmd),0);
if(!bytes) { // closed by peer
close(*socket);
return;
}
if(bytes < 0 || cmd[bytes-1] == 10 || cmd[bytes-1] == 13) {
if(errno == EINTR)
continue;
sprintf(msg,"Error: receiving from %s.\r\n",
address);
close(*socket);
return;
}
if(strcmp(cmd,"exit\r\n") == 0) {
break;
} else if(strcmp(cmd,"help\r\n") == 0) {}
// ...
}
This code obviously ignores the possibility of multiple commands being read in a single recv (i.e., the buffer being "help\r\ncmd\r\nX\r\nexit\r\n")... but you'll solve that at some point.
This has a logic problem:
while((bytes = recv(*socket,cmd,sizeof(cmd),0)) > 0) {
if(bytes < 0) {
}
}
bytes will be always greater than zero so the if(bytes<0){} block will never
execute.
You may want to change it to
while((bytes = recv(*socket,cmd,sizeof(cmd),0))) {
if(bytes < 0) {
}
}
If bytes equals to zero, it will not enter while loop.
I'm (synchronously) reading serial input in Windows using ReadFile(), but instead of waiting for the serial port to have input then returning that as I thought it should, ReadFile() instead returns immediately with a value of FALSE, and a GetLastError() of 0. (Yes, I'm certain I have the right error code and am not making syscalls in between).
The ReadFile() documentation says that when the function "is completing asynchronously, the return value is zero (FALSE)." How is it that a synchronous read can be completing asychronously? Why would this be an error? It's worth noting that the data read is garbage data, as one might expect.
More generally, how can I force ReadFile() to behave like a simple synchronous read of a serial port, or at least behave something like the UNIX read()?
Edit: Here is some source code:
HANDLE my_connect(char *port_name)
{
DCB dcb;
COMMTIMEOUTS timeouts;
HANDLE hdl = CreateFile(port_name,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
0);
GetCommState(port_name, &dcb);
dcb.BaudRate = 115200;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY;
if(SetCommState(hdl, &dcb) == 0)
{
fprintf(stderr, "SetCommState failed with error code %d.\n",
GetLastError());
return (HANDLE) -1;
}
/* TODO: Set a variable timeout. */
timeouts.ReadIntervalTimeout = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.ReadTotalTimeoutConstant = 5000; /* wait 5s for input */
timeouts.WriteTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 5000;
if(SetCommTimeouts(hdl, &timeouts) == 0)
{
fprintf(stderr, "SetCommTimeouts failed with error code %d.\n",
GetLastError());
return (HANDLE) -1;
}
return hdl;
}
int my_disconnect(HANDLE hdl)
{
return CloseHandle(hdl);
}
int my_send(HANDLE hdl, char *cmd)
{
DWORD nb = 0;
if(WriteFile(hdl, cmd, strlen(cmd), &nb, NULL) == 0)
{
fprintf(stderr, "WriteFile failed with error code %d.\n",
GetLastError());
return -1;
}
return (int) nb;
}
int my_receive(HANDLE hdl, char *dst, int dstlen)
{
int i;
DWORD r;
BOOL err;
char c = '\0';
for (i = 0; i < dstlen; err = ReadFile(hdl, &c, 1, &r, NULL))
{
if (err == 0)
{
fprintf(stderr, "ReadFile failed with error code %d.\n",
GetLastError());
return -1;
}
if (r > 0)
{
dst[i++] = c;
if (c == '\n') break;
}
}
if (i == dstlen)
{
fprintf(stderr, "Error: read destination buffer not large enough.\
Recommended size: 256B. Your size: %dB.\n", dstlen);
return -1;
}
else
{
dst[i] = '\0'; /* null-terminate the string. */
}
return i;
}
And my test code:
HANDLE hdl = my_connect("COM4");
char *cmd = "/home\n"; /* basic command */
char reply[256];
my_send(hdl, cmd);
my_receive(hdl, reply, 256);
puts(reply);
It's not completing asynchronously. If it were, GetLastError would return ERROR_IO_PENDING.
To do synchronous I/O, open the file without FILE_FLAG_OVERLAPPED.
It should not be possible for ReadFile to fail without a valid GetLastError code. ReadFile only returns false when the driver sets a non-success status code.
I have server client application.
When I'm sending messages in a row(without scanf in the code below), it's seems the server doesn't get them(doesn't print).
if I wait a little bit(with the scanf in the code below) and then send the next message the server works fine and prints all messages.
what's the problem?
how can I fix it, cause I want to do more with the message(not just to print it) that arrived to the server.
in my client code(where server prints nothing)
char message[(100)] = {0};
int x = rand();
while(i < 3)
{
printf(" I send %d\n", x);fflush(NULL);
sprintf(message, "%d",x);
if( send(mainSockfd, message,strlen(message),0) == -1)
{
printf("ERRRRRORRRR\n");fflush(NULL);
}
i++;
x = rand() % 100;
}
in my client code(when server prints the messages)
char message[(100)] = {0};
int x = rand();
while(i < 3)
{
printf(" I send %d\n", x);fflush(NULL);
sprintf(message, "%d",x);
if( send(mainSockfd, message,strlen(message),0) == -1)
{
printf("ERRRRRORRRR\n");fflush(NULL);
}
i++;
x = rand() % 100;
scanf("%d",&x); // this is the only change
}
in my server code
char command[(100+1)] = {0};
while(1)
{
readLength = recv(sockfd, command, 100+1,0);
if(readLength > 0)
{
printf("arrived = %s,\n",command);fflush(NULL);
ZeroMemory(command, sizeof(command));
}
else if( readLength == 0)
{
break;
}
else if ( readLength < 0 ){
if(GetLastError() == 10035)
{
continue;
}
if(GetLastError() == 10057 || GetLastError() == 10054)
{
break;
}
continue;
}
}
As you seem to be transferring 0-terminated "strings" without the 0 termination, you should read one char less then the read buffer provides to always have the read buffer being 0-terminated, as if you try to printf a non 0-terminated "string" you provoke undefined behaviour.
So change this
readLength = recv(sockfd, command, 100+1,0);
to become this
readLength = recv(sockfd, command, 100,0);
I have two daemons, and A is speaking to B. B is listening on a port, and A opens a tcp connection to that port. A is able to open a socket to B, but when it attempts to actually write said socket, I get a SIGPIPE, so I'm trying to figure out where B could be closing the open socket.
However, if I attach to both daemons in gdb, the SIGPIPE happens before any of the code for handling data is called. This kind of makes sense, because the initial write is never successful, and the listeners are triggered from receiving data. My question is - what could cause daemon B to close the socket before any data is sent? The socket is closed less than a microsecond after opening it, so I'm thinking it can't be a timeout or anything of the sort. I would love a laundry list of possibilities to track down, as I've been chewing on this one for a few days and I'm pretty much out of ideas.
As requested, here is the code that accepts and handles communication:
{
extern char *PAddrToString(pbs_net_t *);
int i;
int n;
time_t now;
fd_set *SelectSet = NULL;
int SelectSetSize = 0;
int MaxNumDescriptors = 0;
char id[] = "wait_request";
char tmpLine[1024];
struct timeval timeout;
long OrigState = 0;
if (SState != NULL)
OrigState = *SState;
timeout.tv_usec = 0;
timeout.tv_sec = waittime;
SelectSetSize = sizeof(char) * get_fdset_size();
SelectSet = (fd_set *)calloc(1,SelectSetSize);
pthread_mutex_lock(global_sock_read_mutex);
memcpy(SelectSet,GlobalSocketReadSet,SelectSetSize);
/* selset = readset;*/ /* readset is global */
MaxNumDescriptors = get_max_num_descriptors();
pthread_mutex_unlock(global_sock_read_mutex);
n = select(MaxNumDescriptors, SelectSet, (fd_set *)0, (fd_set *)0, &timeout);
if (n == -1)
{
if (errno == EINTR)
{
n = 0; /* interrupted, cycle around */
}
else
{
int i;
struct stat fbuf;
/* check all file descriptors to verify they are valid */
/* NOTE: selset may be modified by failed select() */
for (i = 0; i < MaxNumDescriptors; i++)
{
if (FD_ISSET(i, GlobalSocketReadSet) == 0)
continue;
if (fstat(i, &fbuf) == 0)
continue;
/* clean up SdList and bad sd... */
pthread_mutex_lock(global_sock_read_mutex);
FD_CLR(i, GlobalSocketReadSet);
pthread_mutex_unlock(global_sock_read_mutex);
} /* END for each socket in global read set */
free(SelectSet);
log_err(errno, id, "Unable to select sockets to read requests");
return(-1);
} /* END else (errno == EINTR) */
} /* END if (n == -1) */
for (i = 0; (i < max_connection) && (n != 0); i++)
{
pthread_mutex_lock(svr_conn[i].cn_mutex);
if (FD_ISSET(i, SelectSet))
{
/* this socket has data */
n--;
svr_conn[i].cn_lasttime = time(NULL);
if (svr_conn[i].cn_active != Idle)
{
void *(*func)(void *) = svr_conn[i].cn_func;
netcounter_incr();
pthread_mutex_unlock(svr_conn[i].cn_mutex);
func((void *)&i);
/* NOTE: breakout if state changed (probably received shutdown request) */
if ((SState != NULL) &&
(OrigState != *SState))
break;
}
else
{
pthread_mutex_lock(global_sock_read_mutex);
FD_CLR(i, GlobalSocketReadSet);
pthread_mutex_unlock(global_sock_read_mutex);
close_conn(i, TRUE);
pthread_mutex_unlock(svr_conn[i].cn_mutex);
pthread_mutex_lock(num_connections_mutex);
sprintf(tmpLine, "closed connections to fd %d - num_connections=%d (select bad socket)",
i,
num_connections);
pthread_mutex_unlock(num_connections_mutex);
log_err(-1, id, tmpLine);
}
}
else
pthread_mutex_unlock(svr_conn[i].cn_mutex);
} /* END for i */
/* NOTE: break out if shutdown request received */
if ((SState != NULL) && (OrigState != *SState))
return(0);
/* have any connections timed out ?? */
now = time((time_t *)0);
for (i = 0;i < max_connection;i++)
{
struct connection *cp;
pthread_mutex_lock(svr_conn[i].cn_mutex);
cp = &svr_conn[i];
if (cp->cn_active != FromClientDIS)
{
pthread_mutex_unlock(svr_conn[i].cn_mutex);
continue;
}
if ((now - cp->cn_lasttime) <= PBS_NET_MAXCONNECTIDLE)
{
pthread_mutex_unlock(svr_conn[i].cn_mutex);
continue;
}
if (cp->cn_authen & PBS_NET_CONN_NOTIMEOUT)
{
pthread_mutex_unlock(svr_conn[i].cn_mutex);
continue; /* do not time-out this connection */
}
/* NOTE: add info about node associated with connection - NYI */
snprintf(tmpLine, sizeof(tmpLine), "connection %d to host %s has timed out after %d seconds - closing stale connection\n",
i,
PAddrToString(&cp->cn_addr),
PBS_NET_MAXCONNECTIDLE);
log_err(-1, "wait_request", tmpLine);
/* locate node associated with interface, mark node as down until node responds */
/* NYI */
close_conn(i, TRUE);
pthread_mutex_unlock(svr_conn[i].cn_mutex);
} /* END for (i) */
return(0);
}
NOTE: I didn't write this code.
Is it possible you messed up and somewhere else in the program you try to close the same handle twice?
That could do this to you very easily.
HINT: systrace can determine if this is happening.