这个实现方法只能够单线程聊天，recv是阻塞的，你发一句我回一句，必须一来一回，后文会记录多线程实现聊天

客户端代码如下

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(int arg, char *args[])
{
	if (arg < 3)
	{
		return -1;
	}

	int port = atoi(args[2]);
	int st = socket(AF_INET, SOCK_STREAM, 0);//初始化socket

	struct sockaddr_in addr; // 定义一个IP地址的结构
	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;// 设置结构地址类型为TCP/IP地址
	addr.sin_port = htons(port); // 制定一个端口号：8080，htons：将short类型从host字节类型转到net字节类型
	// 将字符类型的IP地址转化为int，赋给addr结构
	//addr.sin_addr.s_addr = inet_addr("127.0.0.1");
	addr.sin_addr.s_addr = inet_addr(args[1]);

	//
	if (connect(st, (struct sockaddr *)&addr, sizeof(addr)) == -1)
	{
		printf("connect failed %s\n", strerror(errno));
		return EXIT_FAILURE;
	}

	char s[1024];
	while (1)
	{
		memset(s, 0, sizeof(1024));
		read(STDIN_FILENO, s, sizeof(s)); // 从键盘读取用户输入
		if (send(st, s, strlen(s), 0) == -1)
		{
			printf("send failed %s\n", strerror(errno));
			return EXIT_FAILURE;
		}

		memset(s, 0, sizeof(s));
		if (recv(st, s, sizeof(s), 0) > 0)// 如果接受数据失败循环结束，这里是阻塞调用，会停在这里等待服务端发送消息，服务端也是一样
			printf("recv %s\n", s);
		else
			break;
	}
	close(st);

	return EXIT_SUCCESS;
}

#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>

int main(int arg, char *args[])
{
	if (arg < 2)
	{
		return -1;
	}
	int port = atoi(args[1]);
	int st = socket(AF_INET, SOCK_STREAM, 0); //初始化socket

	int on = 1;
	if (setsockopt(st, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1)
	{
		printf("setsockopt failed %s\n", strerror(errno));
		return EXIT_FAILURE;
	}

	struct sockaddr_in addr; // 定义一个IP地址结构
	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET; // 将addr结构的属性定位为TCP/IP地址
	addr.sin_port = htons(port); // 将本地字节顺序转化为网络字节顺序
	addr.sin_addr.s_addr = htonl(INADDR_ANY); // INADDR_ANY代表这个server上所有的地址

	// 将ip与server程序绑定
	if (bind(st, (struct sockaddr *) &addr, sizeof(addr)) == -1)
	{
		printf("bind failed %s\n", strerror(errno));
		return EXIT_FAILURE;
	}

	// server端开始listen
	if (listen(st, 20) == -1)
	{
		printf("listen failed %s\n", strerror(errno));
		return EXIT_FAILURE;
	}
	//printf("listen success\n");
	char s[1024];
	int client_st = 0;
	struct sockaddr_in client_addr; // 表示client端的IP地址
	int i;
	for (i = 0; i < 5; i++)
	{
		memset(&client_addr, 0, sizeof(client_addr));
		socklen_t len = sizeof(client_addr);
		// accept会阻塞，直到有客户端连接过来，accept返回client的socket描述符
		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));
		while (1)
		{
			memset(s, 0, sizeof(1024));
			int rc = recv(client_st, s, sizeof(s), 0);// 是阻塞调用，客户端也是一样
			if (rc > 0)
			{
				printf("revc is %s\n", s);
				memset(s, 0, sizeof(s));
				read(STDIN_FILENO, s, sizeof(s));
				send(client_st, s, strlen(s), 0);
			} else
			{
				if (rc == 0)
				{
					printf("client socket closed\n");
				}
				else
				{
					printf("recv failed %s\n", strerror(errno));
				}
				break;
			}
		}
		close(client_st);


	}
	close(st);
	return 0;
}

.SUFFIXES: .c .o

CC=gcc
ASRCS=sock.c			
BSRCS=server.c
	
AOBJS=$(ASRCS:.c=.o)
BOBJS=$(BSRCS:.c=.o)

AEXEC=client
BEXEC=server

all:$(AOBJS) $(BOBJS)
	$(CC) -o $(AEXEC) $(AOBJS)
	$(CC) -o $(BEXEC) $(BOBJS)
	@echo '-------------ok--------------'

.c.o:
	$(CC) -Wall -g -o $@ -c $< 

clean:
	rm -f $(AOBJS)
	rm -f $(BOBJS)
	rm -f core*