基于TCP的Socket文件双向传输（可并发）

服务器端：

// file_server.c -- socket文件传输服务器端示例代码
// /
#include<netinet/in.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define HELLO_WORLD_SERVER_PORT    69
#define LENGTH_OF_LISTEN_QUEUE     20
#define BUFFER_SIZE                512
#define FILE_NAME_MAX_SIZE         512

int main(int argc, char **argv)
{
	// set socket's address information
	// 设置一个socket地址结构server_addr,代表服务器internet的地址和端口
	struct sockaddr_in   server_addr;
	bzero(&server_addr, sizeof(server_addr));
	server_addr.sin_family = AF_INET;
	server_addr.sin_addr.s_addr = htons(INADDR_ANY);
	server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);

	//用于并发服务器
	pid_t pid;
	
	// create a stream socket
	// 创建用于internet的流协议(TCP)socket，用server_socket代表服务器向客户端提供服务的接口
	int server_socket = socket(PF_INET, SOCK_STREAM, 0);
	if (server_socket < 0)
	{
		printf("Create Socket Failed!\n");
		exit(1);
	}

	// 把socket和socket地址结构绑定
	if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)))
	{
		printf("Server Bind Port: %d Failed!\n", HELLO_WORLD_SERVER_PORT);
		exit(1);
	}

	// server_socket用于监听
	if (listen(server_socket, LENGTH_OF_LISTEN_QUEUE))
	{
		printf("Server Listen Failed!\n");
		exit(1);
	}

	// 服务器端一直运行用以持续为客户端提供服务
	while(1)
	{
		// 定义客户端的socket地址结构client_addr，当收到来自客户端的请求后，调用accept
		// 接受此请求，同时将client端的地址和端口等信息写入client_addr中
		struct sockaddr_in client_addr;
		socklen_t          length = sizeof(client_addr);

		// 接受一个从client端到达server端的连接请求,将客户端的信息保存在client_addr中
		// 如果没有连接请求，则一直等待直到有连接请求为止，这是accept函数的特性，可以
		// 用select()来实现超时检测
		// accpet返回一个新的socket,这个socket用来与此次连接到server的client进行通信
		// 这里的new_server_socket代表了这个通信通道
		int new_server_socket = accept(server_socket, (struct sockaddr*)&client_addr, &length);
		
	  if ((pid = fork()) == 0)
	  {
				close(server_socket);
		
		
		
		if (new_server_socket < 0)
		{
			printf("Server Accept Failed!\n");
			break;
		}
		char status[4];
		recv(new_server_socket, status, sizeof(status), 0);
		printf("recv status from client: %s\n", status);
		
		
		char buffer[BUFFER_SIZE];
		char ack[50];
		
		bzero(buffer, sizeof(buffer));
		length = recv(new_server_socket, buffer, BUFFER_SIZE, 0);//从客户端接收数据，数据是文件名。
		printf("recv file_name from client: %s\n", buffer);
	
		fgets(ack, 4096, stdin);
		send(new_server_socket, ack, strlen(ack), 0);	
		
		
		//sleep(10);
	//	bzero(buffer, sizeof(buffer));
		
		
		
		
		if (length < 0)
		{
			printf("Server Recieve Data Failed!\n");
			break;
		}

		
		
		char file_name[FILE_NAME_MAX_SIZE + 1];   
		bzero(file_name, sizeof(file_name));
		strncpy(file_name, buffer,
				strlen(buffer) > FILE_NAME_MAX_SIZE ? FILE_NAME_MAX_SIZE : strlen(buffer));
		//拷贝字符串
		FILE *fp;
	if(!strcmp(status, "get"))
	{
		
		fp = fopen(file_name, "r");
		if (fp == NULL)
		{
			printf("File:\t%s Not Found!\n", file_name);
		}
		else
		{
			bzero(buffer, BUFFER_SIZE);//清空
			int file_block_length = 0;
			while( (file_block_length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
			{
				printf("file_block_length = %d\n", file_block_length);
				//每次读1024个字节的字符， 就将其发送出去；
				//发送buffer中的字符串到new_server_socket,实际上就是发送给客户端
				if (send(new_server_socket, buffer, file_block_length, 0) < 0)
				{
					printf("Send File:\t%s Failed!\n", file_name);
					break;
				}

				bzero(buffer, sizeof(buffer));
			}
			fclose(fp);
			printf("Recieve File: %s from client:%s\t port: %d Finished!\n", file_name, inet_ntop(AF_INET, &client_addr.sin_addr,buffer,sizeof(buffer)), ntohs(client_addr.sin_port)); 
			printf("File:\t%s Transfer Finished!\n", file_name);
		}
	}
	else
	{
		  fp = fopen(file_name, "w");  
    if (fp == NULL)  
    {  
        printf("File:\t%s Can Not Open To Write!\n", file_name);  
        exit(1);  
    }  
  
    // 从客户端接收数据到buffer中   
    bzero(buffer, sizeof(buffer));  
    int length = 0;  
    while(length = recv(new_server_socket, buffer, BUFFER_SIZE, 0))  
    {  
        if (length < 0)  
        {  
            printf("Recieve Data   Failed!\n");  
            break;  
        }  
		else
			printf("%s\n", buffer);	
        int write_length = fwrite(buffer, sizeof(char), length, fp);  
        if (write_length < length)  
        {  
            printf("File:\t%s Write Failed!\n", file_name);  
            break;  
        }  
        bzero(buffer, BUFFER_SIZE);  
    }  
	fclose(fp);
  
    printf("Recieve File: %s from client:%s\t port: %d Finished!\n", file_name, inet_ntop(AF_INET, &client_addr.sin_addr,buffer,sizeof(buffer)), ntohs(client_addr.sin_port));  
		
	}
	close(new_server_socket);	
    exit(0);
	  }
	  close(new_server_socket);
  }
	//close(new_server_socket);
	//close(server_socket);

	return 0;
}

客户端：

//  
// file_client.c  socket传输文件的client端示例程序   
// ///  
#include<netinet/in.h>                         // for sockaddr_in  
#include<sys/types.h>                          // for socket  
#include<sys/socket.h>                         // for socket  
#include<stdio.h>                              // for printf  
#include<stdlib.h>                             // for exit  
#include<string.h>                             // for bzero  
  
#define HELLO_WORLD_SERVER_PORT       69  
#define BUFFER_SIZE                   512  
#define FILE_NAME_MAX_SIZE            512  
  
int main(int argc, char **argv)  
{  
    if (argc != 2)  
    {  
        printf("Usage: ./%s ServerIPAddress\n", argv[0]);  
        exit(1);  
    }  
  
    // 设置一个socket地址结构client_addr, 代表客户机的internet地址和端口  
    struct sockaddr_in client_addr;  
    bzero(&client_addr, sizeof(client_addr));  
    back:client_addr.sin_family = AF_INET; // internet协议族 

	 //inet_aton(rand(), &client_addr.sin_addr.s_addr);
	 //  printf("IPstr:%s\n",inet_ntoa(*((struct in_addr*)&client_addr.sin_addr.s_addr)));
	  client_addr.sin_addr.s_addr = htons(INADDR_ANY); // INADDR_ANY表示自动获取本机地址  


    client_addr.sin_port = htons(0); // auto allocated, 让系统自动分配一个空闲端口  
  
    // 创建用于internet的流协议(TCP)类型socket，用client_socket代表客户端socket  
    int client_socket = socket(AF_INET, SOCK_STREAM, 0);  
    if (client_socket < 0)  
    {  
        printf("Create Socket Failed!\n");  
        exit(1);  
    }  
  
    // 把客户端的socket和客户端的socket地址结构绑定   
    if (bind(client_socket, (struct sockaddr*)&client_addr, sizeof(client_addr)))  
    {  
        printf("Client Bind Port Failed!\n");  
        exit(1);  
    }  
  
    // 设置一个socket地址结构server_addr,代表服务器的internet地址和端口  
    struct sockaddr_in  server_addr;  
    bzero(&server_addr, sizeof(server_addr));  
    server_addr.sin_family = AF_INET;  
    char buffer[BUFFER_SIZE]; 
    // 服务器的IP地址来自程序的参数   
    if (inet_aton(argv[1], &server_addr.sin_addr) == 0)  
    {  
        printf("Server IP Address Error!\n");  
        exit(1);  
    }  
  
    server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT);  
    socklen_t server_addr_length = sizeof(server_addr);  
  
    // 向服务器发起连接请求，连接成功后client_socket代表客户端和服务器端的一个socket连接  
    if (connect(client_socket, (struct sockaddr*)&server_addr, server_addr_length) < 0)  
    {  
        printf("Can Not Connect To %s!\n", argv[1]);  
        exit(1);  
    }  
	
	else
	{	
	printf("socket 连接成功.\n");
	printf("server:%s\t port: %d connected!\n",inet_ntop(AF_INET, &server_addr.sin_addr,buffer,sizeof(buffer)), ntohs(server_addr.sin_port)); 
	}
	char status[4];
	printf(" input get ? \t put ?;\n");
	//fgets(status, 4096, stdin);  反正用这个是错误的？原因不详。
	//bzero(status, sizeof(status));  
	scanf("%s", status);
	printf("status == %s\n", status);
	send(client_socket, status, sizeof(status), 0);
	
	
    char file_name[FILE_NAME_MAX_SIZE + 1];  
    bzero(file_name, sizeof(file_name));  
    printf("Please Input File Name .\t");  
    scanf("%s", file_name);  
	printf("输入的文件名为：%s\n",file_name);

   
	char recvline[BUFFER_SIZE];
    bzero(buffer, sizeof(buffer));  
    strncpy(buffer, file_name, strlen(file_name) > BUFFER_SIZE ? BUFFER_SIZE : strlen(file_name));  
		
    // 向服务器发送buffer中的数据，此时buffer中存放的是客户端需要接收(发送)的文件的名字  
    send(client_socket, buffer, BUFFER_SIZE, 0);
   
    recv(client_socket, recvline, 1024, 0);
    printf("recv ack from server: %s\n", recvline);
	FILE *fp;
if(!strcmp(status, "get")) //下载文件；
{
	
    fp = fopen(file_name, "w");  
    if (fp == NULL)  
    {  
        printf("File:\t%s Can Not Open To Write!\n", file_name);  
        exit(1);  
    }  
  
    // 从服务器端接收数据到buffer中   
    bzero(buffer, sizeof(buffer));  
    int length = 0;  
    while(length = recv(client_socket, buffer, BUFFER_SIZE, 0))  
    {  
        if (length < 0)  
        {  
            printf("Recieve Data From Server %s Failed!\n", argv[1]);  
            break;  
        }  
		else
			printf("%s\n", buffer);			
		
        int write_length = fwrite(buffer, sizeof(char), length, fp);  
        if (write_length < length)  
        {  
            printf("File:\t%s Write Failed!\n", file_name);  
            break;  
        }  
        bzero(buffer, BUFFER_SIZE);  
    }  
  
    printf("Recieve File:\t %s From Server[%s] Finished!\n", file_name, argv[1]);  

}
else //else 上传
{
		fp = fopen(file_name, "r");
		if (fp == NULL)
		{
			printf("File:\t%s Not Found!\n", file_name);
		}
		else
		{
			bzero(buffer, BUFFER_SIZE);//清空
			int file_block_length = 0;
			while( (file_block_length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
			{
				printf("file_block_length = %d\n", file_block_length);
				//每次读1024个字节的字符， 就将其发送出去；
				//发送buffer中的字符串到 client_socket,实际上就是发送给fuwu端
				if (send(client_socket, buffer, file_block_length, 0) < 0)
				{
					printf("Send File:\t%s Failed!\n", file_name);
					break;
				}

				bzero(buffer, sizeof(buffer));
			}
			//fclose(fp);   //报错 double  free 
			printf("File:\t%s Transfer Finished!\n", file_name);
		}
		//goto back;
	
}
  
    // 传输完毕，关闭socket   
    fclose(fp);  
    close(client_socket);  
	goto back;
    return 0;  
  
}