C socket: recv and send all data - c

I would like to obtain a behavior similar to this:
Server run
Client run
Client type a command like "help" or other
Server responds appropriately
go to 3
The problem is that when my function excCommand("help") run just a little text is received and printed.
My text file is this:
COMMAND HELP:
help - Display help
quit - Shutdown client
only COMMAND HELP is printed.
Another problem is that when i type a command nothing is printed and after 2 command client exit.
This is the piece in particular:
while (quit)
{
getLine("client> ", command, 10);
if (strcmp(command, "quit") == 0)
quit = 0;
else
excCommand(command);
}
This is the server:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "common.h"
int main(int argc, char *argv[])
{
if (argc != 2)
ErrorWithUserMessage("Parameter(s)", "<Server Port>");
char *service = argv[1];
int servSock = SetupTCPServerSocket(service);
if (servSock < 0)
ErrorWithUserMessage("SetupTCPServerSocket() failed: ", "unable to establish");
unsigned int childProcessCount = 0;
while (1)
{
int clntSock = AcceptTCPConnection(servSock);
pid_t processID = fork();
if (processID < 0)
ErrorWithSystemMessage("fork() failed");
else if (processID == 0)
{
close(servSock);
HandleTCPClient(clntSock);
exit(EXIT_SUCCESS);
}
printf("with child process: %d\n", processID);
close(clntSock);
childProcessCount++;
//clean up zombies
while (childProcessCount)
{
processID = waitpid((pid_t) - 1, NULL, WNOHANG);
if (processID < 0)
ErrorWithSystemMessage("waitpid() failed");
else if (processID == 0)
break;
else
childProcessCount--;
}
}
}
Handler:
void HandleTCPClient(int clntSock)
{
char buffer[BUFSIZE];
ssize_t numBytesRcvd = recv(clntSock, buffer, BUFSIZE, 0);
buffer[numBytesRcvd] = '\0';
if (numBytesRcvd < 0)
ErrorWithSystemMessage("recv() failed");
if (strcmp(buffer, "help") == 0)
{
FILE *fp = fopen("help.txt", "r");
if (fp)
{
char line[128];
while (fgets(line, sizeof(line), fp) != NULL)
{
if (send(clntSock, line, sizeof(line), 0) < 0)
ErrorWithSystemMessage("send() failed");
}
fclose(fp);
}
}
close(clntSock);
}
and this is my client:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "common.h"
int sock;
void getLine(char *message, char *buf, int maxLen)
{
printf("%s", message);
fgets(buf, maxLen, stdin);
buf[strlen(buf) - 1] = 0;
}
void excCommand(char *command)
{
if ( send(sock, command, strlen(command), 0) < 0)
ErrorWithSystemMessage("send() failed");
char replyMessage[BUFSIZE];
ssize_t numBytesRecv = 0;
do
{
numBytesRecv = recv(sock, replyMessage, BUFSIZE, 0);
if ( numBytesRecv < 0)
ErrorWithSystemMessage("recv() failed");
printf("%s\n", replyMessage);
memset(&replyMessage, 0, sizeof(replyMessage));
}
while (numBytesRecv > 0);
}
void PrintFile(const char *filename)
{
FILE *fp;
fp = fopen(filename, "r");
if (fp)
{
char line[128];
while (fgets(line, sizeof(line), fp) != NULL)
fputs(line, stdout);
fputs("\n", stdout);
fclose(fp);
}
}
int main(int argc, char *argv[])
{
int quit = 1;
char command[10];
if (argc < 2 || argc > 3)
{
ErrorWithUserMessage("Parameter(s)", "<Server Address> <Server Port>");
}
char *server = argv[1];
char *service = argv[2];
sock = SetupTCPClientSocket(server, service);
if (sock < 0)
ErrorWithUserMessage("SetupTCPClientSocket() failed: ", "unable to connect");
printf("Connection established!\n\n");
PrintFile("menu.txt");
excCommand("help");
while (quit)
{
getLine("client> ", command, 10);
if (strcmp(command, "quit") == 0)
quit = 0;
else
excCommand(command);
}
fputs("\n", stdout);
close(sock);
exit(EXIT_SUCCESS);
}
sorry for being so long-winded

The recv() and send() functions do not guarantee to send/recv all data (see man recv, man send)
You need to implement your own send_all() and recv_all(), something like
bool send_all(int socket, void *buffer, size_t length)
{
char *ptr = (char*) buffer;
while (length > 0)
{
int i = send(socket, ptr, length);
if (i < 1) return false;
ptr += i;
length -= i;
}
return true;
}
The following guide may help you Beej's Guide to Network Programming

Usual problems.
void excCommand(char *command)
{
if ( send(sock, command, strlen(command), 0) < 0)
ErrorWithSystemMessage("send() failed");
char replyMessage[BUFSIZE];
ssize_t numBytesRecv = 0;
do
{
numBytesRecv = recv(sock, replyMessage, BUFSIZE, 0);
if ( numBytesRecv < 0)
ErrorWithSystemMessage("recv() failed");
printf("%s\n", replyMessage);
Invalid. numBytesRecv could have been zero, in which case there is no message at all, otherwise at this point must be positive, as you've already tested for negative, and it indicates the actual length of the message, which isn't necessarily null-terminated. Change to:
if (numBytesRecv == 0)
break;
printf("%.*s\n", numBytesRecv, replyMessage);
and then:
memset(&replyMessage, 0, sizeof(replyMessage));
Pointless. Remove.
}
while (numBytesRecv > 0);
At this point you should check for numBytesRecv < 0 and call perror() or one of its friends.

I choose to send before each send() if i have to continue or not.
so i first have 3 define
#define BUFFSIZE 1024
#define CONT "CONT"
#define DONE "DONE"
Then to send my data
int send_to_socket(int sock, char *msg)
{
size_t len;
int ret[2];
len = strlen(msg);
ret[0] = send(sock, (len <= BUFFSIZE) ? DONE : CONT, 4, 0);
ret[1] = send(sock, msg, BUFFSIZE, 0);
if (ret[0] <= 0 || ret[1] <= 0)
{
perror("send_to_socket");
return (-1);
}
if (len > BUFFSIZE)
return (send_to_socket(sock, msg + BUFFSIZE));
return (1);
}
And to receive it :
char *recv_from_socket(int cs)
{
char state[5];
char buff[BUFFSIZE+1];
char *msg;
int ret[2];
msg = NULL;
while (42)
{
bzero(state, 5);
bzero(buff, BUFFSIZE+1);
ret[0] = recv(cs, state, 4, 0);
ret[1] = recv(cs, buff, BUFFSIZE, 0);
if (ret[0] <= 0 || ret[1] <= 0)
{
perror("recv_from_socket");
return (NULL);
}
// strfljoin() is selfmade
// join the string and free the left argument to prevent memory leaks.
// return fresh new string
msg = (msg) ? ft_strfljoin(msg, buff) : strdup(buff);
if (strncmp(state, DONE, 4) == 0)
break ;
i++;
}
return (msg);
}

Related

testing the program for various memory allocation errors and memory leaks

The tee utility copies its standard input to both stdout and to a file. This allows the user to view the output of a command on the console while writing a log to a file at the same time.
My program implements the tee command from linux POSIX system calls, with the -a option.
How can I modify the program to test for possible memory allocation errors? Positive memory leaks.
Also, the memory allocation doesn't seem right to me. When creating a new buffer each time I call getline(), should I declare and initialize line outside the loop and reallocate it only after the loop has ended?
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <fcntl.h>
#include <sys/stat.h>
#include "apue.h"
int writeAll(int fd, char *buf, int buflen);
int main(int argc, char *argv[]) {
struct stat status;
int option;
bool append = false;
int errCode = 0;
while ((option = getopt(argc, argv, "a")) != -1) {
switch (option) {
case 'a':
append = true;
break;
}
}
// We need to write in all the files given as parameter AND stdout.
int numFileDescriptors = argc - optind + 1;
int *fileDescriptors = malloc((numFileDescriptors + 1) * sizeof(*fileDescriptors));
char **fileNames = malloc((numFileDescriptors + 1) * sizeof(*fileNames));
int lastFileDescriptor = 0;
fileDescriptors[0] = STDOUT_FILENO;
fileNames[0] = "stdout";
int flags = O_CREAT | O_WRONLY;
if (append) {
flags = flags | O_APPEND;
} else {
flags = flags | O_TRUNC;
}
for (int i = optind; i < argc; i++) {
if (access(argv[i], F_OK) == 0) {
if (access(argv[i], W_OK) < 0) {
err_msg("%s: Permission denied", argv[i]);
errCode = 1;
continue;
}
}
if (lstat(argv[i], &status) < 0) {
status.st_mode = 0;
}
if (S_ISDIR(status.st_mode)) {
err_msg("%s: Is a directory", argv[i]);
errCode = 1;
continue;
}
int fd = open(argv[i], flags, 0644);
if (fd < 0) {
err_msg("%s: Failed to open", argv[i]);
errCode = 1;
continue;
}
lastFileDescriptor = lastFileDescriptor + 1;
fileDescriptors[lastFileDescriptor] = fd;
fileNames[lastFileDescriptor] = argv[i];
}
while (true) {
size_t len = 0;
ssize_t read = 0;
char *line = NULL;
read = getline(&line, &len, stdin);
if (read == -1) {
break;
}
for (int i = 0; i <= lastFileDescriptor; i++) {
int written = writeAll(fileDescriptors[i], line, strlen(line));
if (written < 0) {
err_msg("%s: Failed to write", fileNames[i]);
errCode = 1;
}
}
}
for (int i = 0; i <= lastFileDescriptor; i++) {
close(fileDescriptors[i]);
}
free(fileDescriptors);
free(fileNames);
return errCode;
}
int writeAll(int fd, char *buf, int buflen) {
ssize_t written = 0;
while (written < buflen) {
int writtenThisTime = write(fd, buf + written, buflen - written);
if (writtenThisTime < 0) {
return writtenThisTime;
}
written = written + writtenThisTime;
}
return written;
}
Testing for memory allocation failure is simple: just add tests, report the failure and exit with a non zero exit status.
To avoid memory leaks, you must free the line that was allocated by getline inside the while (true) loop:
while (true) {
size_t len = 0;
char *line = NULL;
ssize_t nread = getline(&line, &len, stdin);
if (nread == -1) {
if (errno == ENOMEM) {
fprintf(stderr, "out of memory\n");
exit(1);
}
free(line);
break;
}
for (int i = 0; i <= lastFileDescriptor; i++) {
int written = writeAll(fileDescriptors[i], line, nread);
if (written < 0) {
err_msg("%s: Failed to write", fileNames[i]);
errCode = 1;
}
}
free(line);
}
Alternately, you can reuse the same line for the next iteration and only free the buffer after the while loop:
size_t len = 0;
char *line = NULL;
while (true) {
ssize_t nread = getline(&line, &len, stdin);
if (nread == -1) {
if (errno == ENOMEM) {
fprintf(stderr, "out of memory\n");
exit(1);
}
break;
}
for (int i = 0; i <= lastFileDescriptor; i++) {
int written = writeAll(fileDescriptors[i], line, nread);
if (written < 0) {
err_msg("%s: Failed to write", fileNames[i]);
errCode = 1;
}
}
}
free(line);
Note that reading a full line at a time is risky as the input might contain very long, possibly unlimited lines (eg: /dev/zero). You might want to use fgets() to read a line with a limited length and dispatch the contents as you read, possibly splitting long lines:
char line[4096];
while (fgets(line, sizeof line, stdin)) {
size_t len = strlen(line);
for (int i = 0; i <= lastFileDescriptor; i++) {
int written = writeAll(fileDescriptors[i], line, len);
if (written < 0) {
err_msg("%s: Failed to write", fileNames[i]);
errCode = 1;
}
}
}
The above code has a limitation: if the input streams contains null bytes, they will cause some data to be lost in translation. A solution is to not use fgets(), but getchar() directly:
for (;;) {
char line[4096];
size_t len = 0;
int c;
while (len < sizeof(line) && (c = getchar()) != EOF)) {
if ((line[len++] = c) == '\n')
break;
}
if (len > 0) {
for (int i = 0; i <= lastFileDescriptor; i++) {
int written = writeAll(fileDescriptors[i], line, len);
if (written < 0) {
err_msg("%s: Failed to write", fileNames[i]);
errCode = 1;
}
}
}
if (c == EOF)
break;
}

In c socket, why my server can't receive the whole content?

I am new in this field, and writing one server and client, but it really confusing that I can't get all the content, but some small clip.
My server code:
read(connfd, name, 20);
//recv(connfd,name,1024,0);
char* a=name;
while(a[0]!='\n'){
a++;
}
a[0]='\0';
printf("name:%s\n", name);
read(connfd, size, 20);
printf("size:%s\n", size);
recv(connfd,buf,8192,0);
printf("buf:%s\n", buf);
if((stream = fopen(name,"w+t"))==NULL){
printf("The file was not opened! \n");
}
int write_length = fwrite(buf,sizeof(char),8192,stream);
bzero(buf,8192);
if(put){
char *res="OK\n";
write(connfd, res, 1024);
}
fclose(stream);
and my client code is:
char buffer[8192];
bzero(buffer,8192);
char * put="PUT\n";
if ((write(fd, put, 8192)) <= 0) {
if (errno != EINTR) {
fprintf(stderr, "Write error: %s\n", strerror(errno));
exit(0);
}
}
struct stat st ;
stat( put_name, &st );
char str[100];
sprintf(str, "%d", st.st_size);
int len;
char *current=NULL;
len=strlen(put_name);
char sendname[1024];
strcpy(sendname,put_name);
strcat(sendname,"\n");
write(fd, sendname, 10);
strcat(str,"\n");
write(fd, str, 10);
FILE *stream;
if((stream = fopen(put_name,"r"))==NULL)
{
printf("The file was not opened! \n");
exit(1);
}
int lengsize = 0;
while((lengsize = fread(buffer,1,8192,stream)) > 0){
if(send(fd,buffer,8192,0)<0){
printf("Send File is Failed\n");
break;
}
bzero(buffer, 8192);
}
Now, I can send all content, but can receive part of them. for example, on my mac, server can receive name but the str is neglected, when I printf the str in the server, it shows the content of file. and the content of file is not the whole file content. Some content disappear. Could you tell me why?
The read and write functions are not guaranteed to send or receive the entire message with a single call. Instead, you're expected to sit in a loop, writing the message incrementally until everything has been sent and reading everything incrementally until everything has been read. For example, if you know exactly how much has been sent, you can do this:
char recvBuffer[BUFFER_SIZE];
int bytesRead = 0;
while (bytesRead < BUFFER_SIZE) {
int readThisTime = read(file, recvBuffer + bytesRead, BUFFER_SIZE - bytesRead);
if (readThisTime == -1) {
// handle error...
}
bytesRead += readThisTime;
}
If you don't know exactly how much has been sent, try this:
char recvBuffer[BUFFER_SIZE];
int bytesRead = 0;
while (bytesRead < BUFFER_SIZE) {
int readThisTime = read(file, recvBuffer + bytesRead, BUFFER_SIZE - bytesRead);
if (readThisTime == -1) {
// handle error...
}
if (readThisTime == 0) break; // Done!
bytesRead += readThisTime;
}
You are ignoring the return values of send() and recv(). You MUST check return values!
When sending the file, lengsize receives how many bytes were actually read from the file. Your client is sending too many bytes when lengsize is < 8192 (typically the last block of the file if the file size is not an even multiple of 8192).
But more importantly, although the client is telling the server the file size, the server is ignoring it to know when to stop reading. The server is also ignoring the return value of recv() to know how many bytes were actually received so it knows how many bytes can safely be written to the output file.
Try something more like this instead:
common:
int readData(int s, void *buf, int buflen)
{
int total = 0;
char *pbuf = (char*) buf;
while (buflen > 0) {
int numread = recv(s, pbuf, buflen, 0);
if (numread <= 0) return numread;
pbuf += numread;
buflen -= numread;
total += numread;
}
return total;
}
int sendData(int s, void *buf, int buflen)
{
int total = 0;
char *pbuf = (char*) buf;
while (buflen > 0) {
int numsent = send(s, pbuf, buflen, 0);
if (numsent <= 0) return numsent;
pbuf += numsent;
buflen -= numsent;
total += numsent;
}
return total;
}
int readInt32(int s, int32_t *value)
{
int res = readData(s, value, sizeof(*value));
if (res > 0) *value = ntohl(*value);
return res;
}
int sendInt32(int s, int32_t value)
{
value = htonl(value);
return sendData(s, &value, sizeof(value));
}
char* readStr(int s)
{
int32_t size;
if (readInt32(s, &size) <= 0)
return NULL;
char *str = malloc(size+1);
if (!str)
return NULL;
if (readData(s, str, size) <= 0) {
free(str);
return NULL;
}
str[size] = '\0';
return str;
}
int sendStr(int s, const char *str)
{
int len = strlen(str);
int res = sendInt32(s, len);
if (res > 0)
res = sendData(s, str, len);
return res;
}
server:
char buffer[8192];
char *name = readStr(connfd);
if (!name) {
// error handling ...
sendStr(connfd, "Socket read error");
return;
}
printf("name:%s\n", name);
int32_t filesize;
if (readInt32(connfd, &filesize) <= 0) {
// error handling ...
free(name);
sendStr(connfd, "Socket read error");
return;
}
printf("size:%d\n", filesize);
if ((stream = fopen(name, "wb")) == NULL) {
// error handling ...
printf("The file was not opened!\n");
free(name);
sendStr(connfd, "File not opened");
return;
}
while (filesize > 0) {
int numread = readData(connfd, buf, min(filesize, sizeof(buffer)));
if (numread <= 0) {
// error handling ...
close(stream);
free(name);
sendStr(connfd, "Socket read error");
return;
}
printf("buf:%.*s\n", numread, buf);
if (fwrite(buf, 1, numread, stream) != numread) {
// error handling ...
close(stream);
free(name);
sendStr(connfd, "File write error");
return;
}
filesize -= numread;
}
fclose(stream);
free(name);
sendStr(connfd, "OK");
client:
char buffer[8192];
struct stat st;
if (stat( put_name, &st ) != 0) {
// error handling ...
exit(0);
}
if ((stream = fopen(put_name, "rb")) == NULL) {
// error handling ...
printf("The file was not opened!\n");
exit(0);
}
if (sendStr(fd, put_name) <= 0) {
// error handling ...
close(stream);
exit(0);
}
int32_t filesize = st.st_size;
if (sendInt32(fd, filesize) <= 0) {
// error handling ...
close(stream);
exit(0);
}
int lengsize;
while (filesize > 0) {
lengsize = fread(buffer, 1, min(filesize , sizeof(buffer)), stream);
if (lengsize <= 0) {
printf("Read File Failed\n");
// error handling ...
close(stream);
exit(0);
}
if (sendData(fd, buffer, lengsize) <= 0) {
printf("Send File Failed\n");
// error handling ...
close(stream);
exit(0);
}
filesize -= lengsize;
}
close(stream);
char *resp = readStr(fd);
if (!resp) {
// error handling ...
exit(0);
}
if (strcmp(resp, "OK") == 0)
printf("Send File OK\n");
else
printf("Send File Failed: %s\n", resp);
free(resp);

Server - Browser showes site only after server is terminated

I am trying to programm a small HTTP-Server with fork(). When I connect to it via firefox, it doesn't show the the page, until I terminate the Server.
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <signal.h>
#define LISTEN_MAX 5
#define CONT_MAX 10000
#define PORT 8081
#define MAX_FILE 2
#define S_SHORT 50
#define MAX_CONTENT 1000
#define MAX_HEADER 200
const size_t BUF_LEN = 1024; //was 128
const size_t REQUEST_LEN=1024;
char file_names[MAX_FILE][S_SHORT];
FILE *file_deskriptors[MAX_FILE];
int file_sizes[MAX_FILE];
char file_contents[MAX_FILE][MAX_CONTENT];
// Something unexpected happened. Report error and terminate.
void sysErr( char *msg, int exitCode ) {
fprintf( stderr, "%s\n\t%s\n", msg, strerror( errno ) );
exit( exitCode );
}
// get_line was borrowed from Tiny HTTPd under GPLv2
// https://sourceforge.net/projects/tinyhttpd/?source=typ_redirect
int get_line(int sock, char *buf, int size) {
int i = 0;
char c = '\0';
int n;
while ((i < size - 1) && (c != '\n'))
{
n = recv(sock, &c, 1, 0);
/* DEBUG printf("%02X\n", c); */
if (n > 0)
{
if (c == '\r')
{
n = recv(sock, &c, 1, MSG_PEEK);
/* DEBUG printf("%02X\n", c); */
if ((n > 0) && (c == '\n'))
recv(sock, &c, 1, 0);
else
c = '\n';
}
buf[i] = c;
i++;
}
else
c = '\n';
}
buf[i] = '\0';
return(i);
}
void copyHeaderToBuffer(char *tx_buff, int *status) {
switch(*status) {
case 200: strcpy(tx_buff,"HTTP/1.0 200 OK\r\nContent­type: text/html\r\n\r\n"); break;
}
return;
}
void answer(int *accfd, char *request ) {
int file_size, file_index, status, sent_bytes;
file_size, file_index, status = 0;
char method[S_SHORT], ressource[S_SHORT], proto[S_SHORT];
char tx_buff[MAX_CONTENT+MAX_HEADER];
//rehash query
splitRequest(request, method, ressource, proto);
//check for <GET>
checkMethod(method);
//search the file and get index
getFileIndexByName(ressource, &file_index);
file_size = file_sizes[file_index];
status = getFileStatus(&file_index);
createAnswerMessage(tx_buff, &status, &file_index);
//send the answer
if ( (sent_bytes= write( accfd, tx_buff, strlen(tx_buff))) == -1 ) {
sysErr( "[-] Client Fault: SEND", -4 );
}
return;
}
void createAnswerMessage(char *tx_buff, int *status, int *file_index) {
copyHeaderToBuffer(tx_buff, status);
strcat(tx_buff,file_contents[*file_index]);
strcat(tx_buff,"\r\n");
return;
}
int getFileStatus(int *file_index) {
return 200;
}
void splitRequest(char *request, char *method, char *ressource, char *proto) {
char *temp;
if ((temp = strtok(request, " ")) != NULL) {
strcpy(method, temp);
}
if ((temp = strtok(NULL, " ")) != NULL) {
strcpy(ressource, temp);
}
if ((temp = strtok(NULL, " ")) != NULL) {
strcpy(proto, temp);
}
//remove leading "/" from ressource
cleanRessource(ressource);
return;
}
void cleanRessource(char *ressource) {
if (*ressource == '/') {
printf("\nstr_len_ressource: %i",strlen(ressource));
for ( int i=0; i < strlen(ressource); i++ ) {
ressource[i]=ressource[i+1];
}
}
return;
}
void checkMethod(char *method){
if (strcmp(method, "GET") ) {
printf("\n[-] Error: Method \"%s\" not known .",method);
exit(0);
}
printf("\nincheckMethod method = %s",method);
return;
}
void getFileIndexByName (char *ressource, int *file_index) {
for (int i=0; i<MAX_FILE; i++) {
if ( !strcmp(ressource, file_names[i]) ) {
*file_index = i;
return;
}
}
printf("\[-] Error: File \"%s\" not known.",ressource);
exit(0);
}
void filesInit () {
memset(file_names, '\0', sizeof(file_names));
memset(file_contents, '\0', sizeof(file_contents));
//define your files here:
strcpy(file_names[0],"index.htm");
for (int i=0; i<MAX_FILE; i++) {
//choose only existing files
if (file_names[i][0]!='\0') {
//open file
file_deskriptors[i] = fopen(file_names[i],"r");
//get file size
fseek(file_deskriptors[i], 0, SEEK_END);
file_sizes[i] = ftell(file_deskriptors[i]);
//read the file content to file_contents
fseek(file_deskriptors[i], 0, SEEK_SET);
fread(file_contents[i], 1, CONT_MAX, file_deskriptors[i]);
}
}
return;
}
void filesClose() {
return;
}
int main(int argc, char **argv)
{
//kill childs if recieving SIGCHLD
signal(SIGCHLD,SIG_IGN);
int connfd, accfd;
struct sockaddr_in server_addr, client_addr;
socklen_t sockaddr_len = sizeof(struct sockaddr_in);
//initial the available files on server
filesInit();
// create socket
if ( ( connfd = socket( AF_INET, SOCK_STREAM, 0 ) ) < 0) {
sysErr( "Server Fault : SOCKET", -1 );
}
// Set params so that we receive IPv4 packets from anyone on the specified port
memset( &server_addr, 0, sockaddr_len );
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons( PORT );
//bind socket to port
if ( bind( connfd, (struct sockaddr *) &server_addr, sockaddr_len ) < 0 ) {
sysErr( "\n[-] Server Fault : BIND", -2 );
}else{printf("[+] SERVER ONLINE");}
//let server listen for incoming connections
if ( listen( connfd, LISTEN_MAX) < 0 ) {
sysErr( "[-] Server Fault : LISTEN", -3 );
}
//main loop for accepting clients
while ( true ) {
pid_t pid;
//connecting specific client
if ( (accfd=accept( connfd, (struct sockaddr *) &client_addr, &sockaddr_len )) < 0 ) {
sysErr( "[-] Server Fault : ACCEPT", -4 );
}
//fork & answer
else {
printf("\n[+] CLIENT CONNECTED\n");
switch ( pid = fork() ) {
case -1: {
printf("\n[-] Error while fork()");
return EXIT_FAILURE;
}
case 0: {
int req_line_len=1; //length of request line
int first_line_on = 1; //set first line parameter
char req_line[S_SHORT]; //current read line
char first_line[S_SHORT]; //save first line
memset(req_line, 0, S_SHORT);
memset(first_line, 0, S_SHORT);
printf("\n[+] HTTP REQUEST on accfd: %i",accfd);
//reading line by line from socket
while((req_line_len > 0) && strcmp("\n", req_line)){
req_line_len = get_line( accfd, req_line, S_SHORT-1);
//get first line and save it
if (first_line_on) { first_line_on = 0; strcpy(first_line,req_line); }
if((req_line_len > 0) && strcmp("\n", req_line)) printf("%s",req_line);
}
//answering to client
answer(accfd, first_line);
//close connection
if (!close(accfd)) {printf("\n[+] CONNECTION CLOSED");}
exit(0);
break;
}
default: {
//main process
break;
}
}
}
}
//close listening socket
close( connfd );
//close server files
filesClose();
return 0;
}
The child is terminated, and I get the answer CONNECTION CLOSED
Is there a logical mistake in my Code?
EDIT:
I added a full minimum code.
The "\r\n" I add at to the transmitting msg.
It works fine if I add
close(accfd);
to the main(), but I think it is not actually the problem(only a side effect solution)
the index.htm could be:
<html><body><b>index</b><br>C is a interesting language!</body></html>
When you call fork() the file descriptors of the parent in copied to the child, this is why you can still access the socket in the child process. The network stack will keep the socket alive as long as you have at least one file descriptor open to the socket. You close the socket in the child process but still have it open in the parent.
In other words adding a call to close(accfd) in the parent should fix your problem.

C - irc bot skeleton

#include <winsock2.h>
#include <stdio.h>
const int PORT = 6667;
const char *SERVER = "irc.freenode.org";
const char *CHAN = "#channela";
const char *NICK = "loveMilk";
const int MAX_BUFF_SIZE = 512;
int sock_conn(SOCKET *socketn, const char *HOST, int portn);
int sock_send(SOCKET *socketn, char* msg, ...);
int main(int argc, char *argv[])
{
WSADATA wsadata;
char buff[MAX_BUFF_SIZE];
char oBuff[MAX_BUFF_SIZE];
int buffRec;
if (WSAStartup(MAKEWORD(2,2), &wsadata) != 0)
return 0;
SOCKET sock;
if(sock_conn(&sock, SERVER, PORT) != 0)
{
WSACleanup();
return 0;
}
printf("connected.\n");
sock_send(&sock, "USER %s \"\" \"127.0.0.1\" :%s\r\n", NICK, NICK);
sock_send(&sock, "NICK %s\r\n", NICK);
Sleep(100);
sock_send(&sock, "JOIN %s\r\n", CHAN);
printf("Joined channel.\n");
while(1)
{
memset(buff, 0, MAX_BUFF_SIZE);
memset(oBuff, 0, MAX_BUFF_SIZE);
buffRec = recv(sock, buff, MAX_BUFF_SIZE, 0);
if((buffRec == 0) || (buffRec == SOCKET_ERROR)) break;
if(buff[0] != ':')
{
strcpy(oBuff, "PONG :");
printf("PONG");
sock_send(&sock, oBuff);
}
else
{
if(strstr(buff, "PRIVMSG"))
{
int i, num = 0;
for(i = 0; i < strlen(buff); ++i) if(buff[i] = ' ') ++num;
char** parts = malloc(sizeof(char*) * num);
char *p;
p = strtok(buff, " ");
int j = 0;
while(p != NULL)
{
parts[j] = p;
j++;
p = strtok(NULL, " ");
}
free(parts);
}
}
}
closesocket(sock);
return 1;
}
int sock_conn(SOCKET *socketn, const char *HOST, int portn)
{
WSADATA wsadata;
SOCKADDR_IN sockA;
LPHOSTENT hostE;
if(WSAStartup(MAKEWORD(2,2), &wsadata) == -1) return -1;
if(!(hostE = gethostbyname(HOST)))
{
WSACleanup();
return -1;
}
if ((*socketn = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
{
WSACleanup();
return -1;
}
sockA.sin_family = AF_INET;
sockA.sin_port = htons(portn);
sockA.sin_addr = *((LPIN_ADDR)*hostE->h_addr_list);
if(connect(*socketn, (LPSOCKADDR)&sockA, sizeof(struct sockaddr)) == SOCKET_ERROR)
{
WSACleanup();
return -1;
}
}
int sock_send(SOCKET *socketn, char* msg, ...)
{
char buff[MAX_BUFF_SIZE];
va_list va;
va_start(va, msg);
vsprintf(buff, msg, va);
va_end(va);
send(*socketn, buff, strlen(buff), 0);
return 1;
}
If I try to print buff after the if(strstr(buff, "PRIVMSG")) it crashes.
The while with the strtok won't work, if I try to reach parts[0] it crashes.
I tried to print parts[0] but shows nothing, tried to print during the while loop, shows nothing.
why?
You don't terminate your strings!
Edit the receiving part as this:
buffRec = recv(sock, buff, MAX_BUFF_SIZE, 0);
if((buffRec == 0) || (buffRec == SOCKET_ERROR)) break;
/* New line: Terminate buffer as a string */
buff[buffRec] = '\0';
As the other answer points out, a character array must end with '\0' to be considered a string. I think that C doesn't distinguish between the two, but you need the '\0' to signify the end of string. This could be why strstr(buff, "PRIVMSG")) isn't returning anything. It may default to null (thus not satisfying your if) because it doesn't think it has been passed a string.
'strtok(string, delimiter)' breaks an input string into tokens by using the delimiter. Here, you have passed it NULL as its string and " " as its delimiter. I am unfamiliar with many string functions (still learning C myself), but I think this is incorrect usage in your code.
parts[] does not seem to be defined in the code you've given. Its first use is where you try to store data in it for the inner while loop. Are there any other parts to the program that are not shown?

Read line by line from a socket buffer

I want to write a function that read line by line from a socket buffer obtained from third parameter from read() function from unistd.h header.
I have wrote this:
int sgetline(int fd, char ** out)
{
int buf_size = 128;
int bytesloaded = 0;
char buf[2];
char * buffer = malloc(buf_size);
char * newbuf;
int size = 0;
assert(NULL != buffer);
while( read(fd, buf, 1) > 0 )
{
strcat(buffer, buf);
buf[1] = '\0';
bytesloaded += strlen(buf);
size = size + buf_size;
if(buf[0] == '\n')
{
*out = buffer;
return bytesloaded;
}
if(bytesloaded >= size)
{
size = size + buf_size;
newbuf = realloc(buffer, size);
if(NULL != newbuf)
{
buffer = newbuf;
}
else
{
printf("sgetline() allocation failed!\n");
exit(1);
}
}
}
*out = buffer;
return bytesloaded;
}
but I have some problems with this function, for example, if the input is something like:
HTTP/1.1 301 Moved Permanently\r\n
Cache-Control:no-cache\r\n
Content-Length:0\r\n
Location\r\nhttp://bing.com/\r\n
\r\n\r\n
and I do
int sockfd = socket( ... );
//....
char* tbuf;
while(sgetline(sockfd, &tbuf) > 0)
{
if(strcmp(tbuf,"\r\n\r\n") == 0)
{
printf("End of Headers detected.\n");
}
}
the above C application does not output "End of Header detected.". Why is this, and how can I fix this?
It's not OK to read one byte at a time, because you are making too many system calls - better is to use a buffer, read a chunk and check if you got \n. After getting a line, the rest of the bytes read remains in the buffer, so you cannot mix read/recv with read_line. Another version of read n bytes using this kind of buffer can be write...
My version to read a line, and a little example to use it.
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <string.h>
#define CBSIZE 2048
typedef struct cbuf {
char buf[CBSIZE];
int fd;
unsigned int rpos, wpos;
} cbuf_t;
int read_line(cbuf_t *cbuf, char *dst, unsigned int size)
{
unsigned int i = 0;
ssize_t n;
while (i < size) {
if (cbuf->rpos == cbuf->wpos) {
size_t wpos = cbuf->wpos % CBSIZE;
//if ((n = read(cbuf->fd, cbuf->buf + wpos, (CBSIZE - wpos))) < 0) {
if((n = recv(cbuf->fd, cbuf->buf + wpos, (CBSIZE - wpos), 0)) < 0) {
if (errno == EINTR)
continue;
return -1;
} else if (n == 0)
return 0;
cbuf->wpos += n;
}
dst[i++] = cbuf->buf[cbuf->rpos++ % CBSIZE];
if (dst[i - 1] == '\n')
break;
}
if(i == size) {
fprintf(stderr, "line too large: %d %d\n", i, size);
return -1;
}
dst[i] = 0;
return i;
}
int main()
{
cbuf_t *cbuf;
char buf[512];
struct sockaddr_in saddr;
struct hostent *h;
char *ip;
char host[] = "www.google.com";
if(!(h = gethostbyname(host))) {
perror("gethostbyname");
return NULL;
}
ip = inet_ntoa(*(struct in_addr*)h->h_addr);
cbuf = calloc(1, sizeof(*cbuf));
fprintf(stdout, "Connecting to ip: %s\n", ip);
if((cbuf->fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
return 1;
}
memset(&saddr, 0, sizeof(saddr));
saddr.sin_family = AF_INET;
saddr.sin_port = htons(80);
inet_aton(ip, &saddr.sin_addr);
if(connect(cbuf->fd, (struct sockaddr*)&saddr, sizeof(saddr)) < 0) {
perror("connect");
return 1;
}
snprintf(buf, sizeof(buf), "GET / HTTP/1.1\r\nHost: %s\r\nConnection: close\r\n\r\n", host);
write(cbuf->fd, buf, strlen(buf));
while(read_line(cbuf, buf, sizeof(buf)) > 0) {
// if it's an empty \r\n on a line, header ends //
if(buf[0]=='\r' && buf[1] == '\n') {
printf("------------------------\n");
}
printf("[%s]", buf);
}
close(cbuf->fd);
free(cbuf);
return 0;
}
Try this implementation instead:
int sgetline(int fd, char ** out)
{
int buf_size = 0;
int in_buf = 0;
int ret;
char ch;
char * buffer = NULL;
char * new_buffer;
do
{
// read a single byte
ret = read(fd, &ch, 1);
if (ret < 1)
{
// error or disconnect
free(buffer);
return -1;
}
// has end of line been reached?
if (ch == '\n')
break; // yes
// is more memory needed?
if ((buf_size == 0) || (in_buf == buf_size))
{
buf_size += 128;
new_buffer = realloc(buffer, buf_size);
if (!new_buffer)
{
free(buffer);
return -1;
}
buffer = new_buffer;
}
buffer[in_buf] = ch;
++in_buf;
}
while (true);
// if the line was terminated by "\r\n", ignore the
// "\r". the "\n" is not in the buffer
if ((in_buf > 0) && (buffer[in_buf-1] == '\r'))
--in_buf;
// is more memory needed?
if ((buf_size == 0) || (in_buf == buf_size))
{
++buf_size;
new_buffer = realloc(buffer, buf_size);
if (!new_buffer)
{
free(buffer);
return -1;
}
buffer = new_buffer;
}
// add a null terminator
buffer[in_buf] = '\0';
*out = buffer; // complete line
return in_buf; // number of chars in the line, not counting the line break and null terminator
}
int sockfd = socket( ... );
//....
char* tbuf;
int ret;
// keep reading until end of headers is detected.
// headers are terminated by a 0-length line
do
{
// read a single line
ret = sgetline(sockfd, &tbuf);
if (ret < 0)
break; // error/disconnect
// is it a 0-length line?
if (ret == 0)
{
printf("End of Headers detected.\n");
free(tbuf);
break;
}
// tbuf contains a header line, use as needed...
free(tbuf);
}
while (true);
You are making things more difficult for yourself than they need to be. You really don't need to do strcats to get the single character you read on each read added at the current position.
But your bug is that the routine returns as soon as it sees a \n, so the string it returns can never contain anything following the first \n.

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