linux下用多线程实现socket服务器和客户端的异步通信
程序员文章站
2022-03-15 21:56:54
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前面介绍了用select函数来实现socket的异步收发数据,但是select函数也有一些缺陷,要使socket能持续地通信,select必须不停地检测,这样进程就会一直阻塞在这里,限制了功能的扩展,这里我们用多线程的方式,另创建两个线程用来发送/接收数据,即可解决这个问题,代码如下:
服务器 server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
void* recvsocket(void *ptr)
{
int fd = *(int *)ptr;
char str[1024];
while (1)
{
memset(str, 0, sizeof(str));
int numbytes = recv(fd, s, sizeof(str), 0);
if (numbytes <= 0)
break;
printf("%s\n", str);
}
return NULL;
}
void* sendsocket(void *ptr)
{
int fd = *(int *)ptr;
char str[1024];
while (1)
{
memset(s, 0, sizeof(str));
read(STDIN_FILENO, str, sizeof(str));
send(fd, str, strlen(str), 0);
}
return NULL;
}
int main(int arg, char *args[])
{
int port = 1234;
int st = socket(AF_INET, SOCK_STREAM, 0);
int opt = SO_REUSEADDR;
setsockopt(st, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(st, (struct sockaddr *) &addr, sizeof(addr)) == -1)
{
printf("bind failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
if (listen(st, 20) == -1)
{
printf("listen failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
printf("listen success\n");
int client_st = 0;
struct sockaddr_in client_addr;
pthread_t thrd1, thrd2;
while (1)
{
memset(&client_addr, 0, sizeof(client_addr));
socklen_t len = sizeof(client_addr);
printf("waiting for client.......\n");
client_st = accept(st, (struct sockaddr*) &client_addr, &len);
if (client_st == -1)
{
printf("accept failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
printf("accept by %s\n", inet_ntoa(client_addr.sin_addr));
pthread_create(&thrd1, NULL, recvsocket, &client_st);
pthread_create(&thrd2, NULL, sendsocket, &client_st);
}
close(st);
return 0;
}
客户端 client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
void* recvsocket(void *ptr)
{
int fd = *(int *)ptr;
char str[1024];
while (1)
{
memset(str, 0, sizeof(str));
int numbytes = recv(fd, s, sizeof(str), 0);
if (numbytes <= 0)
break;
printf("%s\n", str);
}
return NULL;
}
void* sendsocket(void *ptr)
{
int fd = *(int *)ptr;
char str[1024];
while (1)
{
memset(s, 0, sizeof(str));
read(STDIN_FILENO, str, sizeof(str));
send(fd, str, strlen(str), 0);
}
return NULL;
}
int main(int arg, char *args[])
{
int port = 1234;
int st = socket(AF_INET, SOCK_STREAM, 0);
int opt = SO_REUSEADDR;
setsockopt(st, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(st, (struct sockaddr *) &addr, sizeof(addr)) == -1)
{
printf("bind failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
if (listen(st, 20) == -1)
{
printf("listen failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
printf("listen success\n");
int client_st = 0;
struct sockaddr_in client_addr;
pthread_t thrd1, thrd2;
while (1)
{
memset(&client_addr, 0, sizeof(client_addr));
socklen_t len = sizeof(client_addr);
printf("waiting for client.......\n");
client_st = accept(st, (struct sockaddr*) &client_addr, &len);
if (client_st == -1)
{
printf("accept failed %s\n", strerror(errno));
return EXIT_FAILURE;
}
printf("accept by %s\n", inet_ntoa(client_addr.sin_addr));
pthread_create(&thrd1, NULL, recvsocket, &client_st);
pthread_create(&thrd2, NULL, sendsocket, &client_st);
}
close(st);
return 0;
}
创建两个线程并发、并行地工作,分别进行发送/接收数据,(其实仅用创建一个线程,在主线程也可以完成相应的发送和接收),但是这样也有一个缺点,那就是如果要在异步通信程序上扩展其他的功能,那么接收数据的工作最好全部由接收数据的线程来完成,因为如果在其他线程中加入recv语句接收数据,那么线程之间会争抢资源,这样就无法判断是哪一个线程接收到了数据。
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