实现TCP服务器端多路并发的方法有①多进程②多线程③IO多路复用（select poll epoll函数）

1.多进程实现并发模式（仅在服务器端更改之前代码实现）

服务器端
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/in.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>

#define SIZE 128

void handler(int sign);
int main(int argc, const char *argv[])
{
if(argc<2){
printf("Usrmsg:%s <Port>\n",argv[0]);
return -1;
}
//1.创建套接字文件，用于链接
int socket_fd;
socket_fd = socket(AF_INET,SOCK_STREAM,0);
if(socket_fd == -1){
perror("socket");
return -1;
}
printf("socket Created ok\n");

//填充结构体sockaddr_in,用于传参
int bind_fd;
struct sockaddr_in serveraddr,connectaddr; //定义填充的结构体
bzero((void *)&serveraddr, sizeof(serveraddr));
serveraddr.sin_family = AF_INET; //IPV4协议
serveraddr.sin_port = htons(atoi(argv[1])); //本地端口号转化位网络字节码
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);//本地IP转化位网络字节码,任意IP
//2.绑定socket文件描述符、端口、IP
bind_fd = bind(socket_fd,(struct sockaddr*)&serveraddr,sizeof(serveraddr));
if(bind_fd == -1){
perror("bind");
return -1;
}
printf("bind ok\n");

//3.监听，将套接字文件属性该主动为被动模式
int listen_fd;
listen_fd = listen(socket_fd,10);

if(listen_fd == -1){
perror("listen");
return -1;
}
printf("listen ok\n");

int addrsize = sizeof(connectaddr);
int accept_fd;
int recvbyte;

char bufrecv[SIZE] = {0};
while(1){

accept_fd = accept(socket_fd,(struct sockaddr*)&connectaddr,&addrsize);
if(accept_fd == -1){
perror("accept");
return -1;
}

printf("connect ok\n");
pid_t pid = fork();

if(pid < 0){
perror("fork");
return -1;
}

if(pid == 0){
close(socket_fd);
while(1){
memset(bufrecv,0,SIZE);
int port = ntohs(connectaddr.sin_port);
char *ip = (char *)(inet_ntoa(connectaddr.sin_addr.s_addr));

recvbyte = recv(accept_fd, bufrecv,sizeof(bufrecv),0);

if(recvbyte <= 0){
printf("client failed connect\n");
return -1;
}
printf("IP:%s Port:%d online. send: %s\n",ip,port,bufrecv);
}
// close(accept_fd);
}
else{
close(accept_fd);
signal(SIGCHLD,handler);

}
}

close(socket_fd);

return 0;
}
void handler(int sign){

waitpid(-1,NULL,WNOHANG);
printf("signal = %d\n",sign);
}

2.多线程实现并发

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/in.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>

#define SIZE 128

void *connectfun(void *arg);
int main(int argc, const char *argv[])
{
if(argc<2){
printf("Usrmsg:%s <Port>\n",argv[0]);
return -1;
}
//1.创建套接字文件，用于链接
int socket_fd;
socket_fd = socket(AF_INET,SOCK_STREAM,0);
if(socket_fd == -1){
perror("socket");
return -1;
}
printf("socket Created ok\n");

//填充结构体sockaddr_in,用于传参
int bind_fd;
struct sockaddr_in serveraddr,connectaddr; //定义填充的结构体
bzero((void *)&serveraddr, sizeof(serveraddr));
serveraddr.sin_family = AF_INET; //IPV4协议
serveraddr.sin_port = htons(atoi(argv[1])); //本地端口号转化位网络字节码
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);//本地IP转化位网络字节码,任意IP
//2.绑定socket文件描述符、端口、IP
bind_fd = bind(socket_fd,(struct sockaddr*)&serveraddr,sizeof(serveraddr));
if(bind_fd == -1){
perror("bind");
return -1;
}
printf("bind ok\n");

//3.监听，将套接字文件属性该主动为被动模式
int listen_fd;
listen_fd = listen(socket_fd,10);

if(listen_fd == -1){
perror("listen");
return -1;
}
printf("listen ok\n");

int addrsize = sizeof(connectaddr);
int accept_fd;

while(1){

accept_fd = accept(socket_fd,(struct sockaddr*)&connectaddr,&addrsize);
if(accept_fd == -1){
perror("accept");
return -1;
}
printf("connect ok\n");

pthread_t pid ;
pthread_create(&pid, NULL,connectfun,(void*)&accept_fd);

}

close(socket_fd);
return 0;

}
void *connectfun(void *arg){
pthread_detach(pthread_self());
char bufrecv[SIZE] = {0};
int recvbyte;
while(1){

memset(bufrecv,0,SIZE);

recvbyte = recv(*(int *)arg, bufrecv,sizeof(bufrecv),0);

if(recvbyte <= 0){
printf("client failed connect\n");
return NULL;
}
printf("send: %s\n",bufrecv);
}
}

3.select函数实现多并发

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/in.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>

#define SIZE 128

int main(int argc, const char *argv[])
{
if(argc<2){
printf("Usrmsg:%s <Port>\n",argv[0]);
return -1;
}
//1.创建套接字文件，用于链接
int socket_fd;
socket_fd = socket(AF_INET,SOCK_STREAM,0);
if(socket_fd == -1){
perror("socket");
return -1;
}
printf("socket Created ok\n");

//填充结构体sockaddr_in,用于传参
int bind_fd;
struct sockaddr_in serveraddr,connectaddr; //定义填充的结构体
bzero((void *)&serveraddr, sizeof(serveraddr));
serveraddr.sin_family = AF_INET; //IPV4协议
serveraddr.sin_port = htons(atoi(argv[1])); //本地端口号转化位网络字节码
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);//本地IP转化位网络字节码,任意IP
//2.绑定socket文件描述符、端口、IP
bind_fd = bind(socket_fd,(struct sockaddr*)&serveraddr,sizeof(serveraddr));
if(bind_fd == -1){
perror("bind");
return -1;
}
printf("bind ok\n");

//3.监听，将套接字文件属性该主动为被动模式
int listen_fd;
listen_fd = listen(socket_fd,10);

if(listen_fd == -1){
perror("listen");
return -1;
}
printf("listen ok\n");

//创建监听集合
fd_set readfds,tempfds;
//清空集合
FD_ZERO(&readfds);
FD_ZERO(&tempfds);
//将关心的文件描述符加入集合
FD_SET(0,&readfds);
FD_SET(socket_fd,&readfds);

//设置最大监听个数
int maxfd = socket_fd;

int addrsize = sizeof(connectaddr);
int accept_fd;
int recvbyte;
int val;
char bufsend[SIZE] = {0};
char bufrecv[SIZE] = {0};
while(1){

tempfds = readfds;
val = select(maxfd + 1,&tempfds,NULL,NULL,NULL);
//4.阻塞函数，等待客户链接请求，不关心链接的是那个客户端，填NULL
if(val < 0)
{
perror("select failed.");
return -1;
}
int i = 0;
for(i = 0;i<maxfd+1;i++){
if(FD_ISSET(i,&tempfds)){

if(i == 0)
{
fgets(bufsend,sizeof(bufsend),stdin);

send(socket_fd, bufsend, sizeof(bufsend),0);
printf("send ok.\n");
}
if(i == socket_fd)
{
accept_fd = accept(socket_fd,(struct sockaddr*)&connectaddr,&addrsize);
if(accept_fd == -1){
perror("accept");
return -1;
}

printf("accept ok\n");
int port = ntohs(connectaddr.sin_port);
char *ip = (char *)(inet_ntoa(connectaddr.sin_addr.s_addr));
printf("IP:%s Port:%d online.\n",ip,port);
FD_SET(accept_fd,&readfds);
maxfd = maxfd > accept_fd ? maxfd : accept_fd;

}
else{
recvbyte = recv(i, bufrecv,sizeof(bufrecv),0);
if(recvbyte <= 0)
{
FD_CLR(i,&readfds);
close(i);
continue;
}

printf("%s\n",bufrecv);

}
}
}
}

close(socket_fd);
close(accept_fd);
return 0;
}