Многопоточность, потоки, threard, pthread_t,pthread_mutex_lock/unlock, pthread_create

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <pthread.h>
void *recvmg(void *sock)
{
int their_sock = *((int *)sock);
char msg[500];
int len;
while((len = recv(their_sock,msg,500,0)) > 0) {
msg[len] = '\0';
fputs(msg,stdout);
memset(msg,'\0',sizeof(msg));
}
}
int main(int argc, char *argv[])
{
struct sockaddr_in their_addr;
int my_sock;
int their_sock;
int their_addr_size;
int portno;
pthread_t sendt,recvt;
char msg[500];
char username[100];
char res[600];
char ip[INET_ADDRSTRLEN];
int len;
 
if(argc > 3) {
printf("too many arguments");
exit(1);
}
portno = atoi(argv[2]);
strcpy(username,argv[1]);
my_sock = socket(AF_INET,SOCK_STREAM,0);
memset(their_addr.sin_zero,'\0',sizeof(their_addr.sin_zero));
their_addr.sin_family = AF_INET;
their_addr.sin_port = htons(portno);
their_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
 
if(connect(my_sock,(struct sockaddr *)&their_addr,sizeof(their_addr)) < 0) {
perror("connection not esatablished");
exit(1);
}
inet_ntop(AF_INET, (struct sockaddr *)&their_addr, ip, INET_ADDRSTRLEN);
printf("connected to %s, start chatting\n",ip);
pthread_create(&recvt,NULL,recvmg,&my_sock);
while(fgets(msg,500,stdin) > 0) {
strcpy(res,username);
strcat(res,":");
strcat(res,msg);
len = write(my_sock,res,strlen(res));
if(len < 0) {
perror("message not sent");
exit(1);
}
memset(msg,'\0',sizeof(msg));
memset(res,'\0',sizeof(res));
}
pthread_join(recvt,NULL);
close(my_sock);
 
}

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <pthread.h>
struct client_info {
int sockno;
char ip[INET_ADDRSTRLEN];
};
int clients[100];
int n = 0;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 
void sendtoall(char *msg,int curr)
{
int i;
pthread_mutex_lock(&mutex);
 
for(i = 0; i < n; i++) {
if(clients[i] != curr) {
if(send(clients[i],msg,strlen(msg),0) < 0) {
continue;
}
}
}
pthread_mutex_unlock(&mutex);
}
 
void *recvmg(void *sock)
{
struct client_info cl = *((struct client_info *)sock);
 
char msg[500];
int len;
int i;
int j;
 
while((len = recv(cl.sockno,msg,500,0)) > 0) { //пока получаем значения;
msg[len] = '\0'; //очищаем последнее значение msg;
sendtoall(msg,cl.sockno); //выполняем отправку;
memset(msg,'\0',sizeof(msg)); //очищаем сообщение;
}
 
pthread_mutex_lock(&mutex); //блокируем поток
printf("%s disconnected\n",cl.ip); //ошибка
 
for(i = 0; i < n; i++) { 
if(clients[i] == cl.sockno) { // если значение массива равно значению дескриптора
j = i; // приравняй количество клиентов к j
while(j < n-1) { 
clients[j] = clients[j+1]; //количество клиентов равно кл+1
j++; 
}
}
}
n--;
pthread_mutex_unlock(&mutex);
}
 
int main(int argc,char *argv[])
{
 
//создаем две структуры для сокетов
 
struct sockaddr_in my_addr,their_addr;
int my_sock;
int their_sock;
 
 
 
socklen_t their_addr_size;
int portno;
pthread_t sendt,recvt;
char msg[500];
int len;
struct client_info cl;
char ip[INET_ADDRSTRLEN];
if(argc > 2) {
printf("too many arguments");
exit(1);
}
portno = atoi(argv[1]);
 
my_sock = socket(AF_INET,SOCK_STREAM,0);
 
memset(my_addr.sin_zero,'\0',sizeof(my_addr.sin_zero));
 
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(portno);
my_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
 
their_addr_size = sizeof(their_addr);
 
if(bind(my_sock,(struct sockaddr *)&my_addr,sizeof(my_addr)) != 0) {
perror("binding unsuccessful");
exit(1);
}
 
if(listen(my_sock,5) != 0) {
perror("listening unsuccessful");
exit(1);
}
 
while(1) {
if((their_sock = accept(my_sock,(struct sockaddr *)&their_addr,&their_addr_size)) < 0) {
perror("accept unsuccessful");
exit(1);
}
 
pthread_mutex_lock(&mutex);
 
printf("%s connected\n",ip);
cl.sockno = their_sock;
strcpy(cl.ip,ip);
clients[n] = their_sock;
n++;
pthread_create(&recvt,NULL,recvmg,&cl);
 
pthread_mutex_unlock(&mutex);
}
return 0;
}