Segmentation fault - big loop - c++

Question

im having a segmentation fault error testing a client-server file transfer. I have this code on the downloader side (this is where i think the problem is):
else if (info_socket[fds[i].fd] == RECIBIENDO) {
close_conn = FALSE;
buffer = (char*) malloc(1500);
rc = recv(fds[i].fd, buffer, 1500, 0);
if (rc < 0) {
if (errno != EWOULDBLOCK) {
perror(" recv() failed");
close_conn = TRUE;
map<int, info_trans*>::iterator it = descargas.find(fds[i].fd);
descargas.erase(it);
}
} else if (rc == 0) {
close_conn = TRUE;
map<int, info_trans*>::iterator it = descargas.find(fds[i].fd);
descargas.erase(it);
} else {
arch = fopen((directorio + descargas[fds[i].fd]->nombre_archivo).c_str(), "ab");
printf("%s -- %d",(directorio + descargas[fds[i].fd]->nombre_archivo).c_str(),fds[i].fd);
totalEscrito = fwrite(buffer, 1, rc, arch);
descargas[fds[i].fd]->bytes_descargados = descargas[fds[i].fd]->bytes_descargados + totalEscrito;
fclose(arch);
file_descript = open((directorio + descargas[fds[i].fd]->nombre_archivo).c_str(), O_RDONLY);
file_size = get_size_by_fd(file_descript);
file_buffer = (char*) mmap(0, file_size, PROT_READ, MAP_SHARED, file_descript, 0);
MD5((unsigned char*) file_buffer, file_size, result);
mdString = (char*) malloc(33);
for (int r = 0; r < 16; r++)
sprintf(&mdString[r * 2], "%02x", (unsigned int) result[r]);
if (strcmp(mdString, (descargas[fds[i].fd]->md5).c_str()) == 0) {
close_conn = TRUE;
map<int, info_trans*>::iterator it = descargas.find(fds[i].fd);
descargas.erase(it);
}
free(mdString);
free(file_buffer);
close(file_descript);
}
The Server is on a similar loop sending the data. The strange part is that if i run this on my laptop it works, but at the school pc's virtual machine throws the Segmentation fault.
If there is a good way to debug the memory using VMware Player, please tell me too.
Thanks you, and sorry for my english level.

Answer 1

free(file_buffer); is wrong. I guess you meant munmap(file_buffer, file_size);.