C++ 实现json形式的Socket传输图片

大致流程：客户端读取图片，经过Base64编码，转成字符串的形式，保存到json中，通过socket传到服务端，然后Base64解码，再转换成图片

一.服务端

1.main.cpp

#include <iostream>
#include <stdio.h>
#include "Base64_1.h"
#include <winsock2.h>  
#include "json1.hpp"

#pragma comment(lib,"ws2_32.lib")  
using json = nlohmann::json;

char revData[3888888];

bool WritePhotoFile(std::basic_string<TCHAR> strFileName, std::string &strData)
{
	HANDLE hFile;
	hFile = CreateFile(strFileName.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

	if (hFile == INVALID_HANDLE_VALUE)
	{
		return false;
	}

	CBase64 base64;
	
	int datalen(0);
	DWORD dwritelen(0);
	std::string strdcode = base64.Decode(strData.data(), strData.size(), datalen);
	if (!WriteFile(hFile, strdcode.data(), datalen, &dwritelen, NULL))
	{
		CloseHandle(hFile);
		return false;
	}
	CloseHandle(hFile);
	return true;
}



int main(int argc, char* argv[])
{
	//初始化WSA  
	WORD sockVersion = MAKEWORD(2, 2);
	WSADATA wsaData;
	if (WSAStartup(sockVersion, &wsaData) != 0)
	{
		return 0;
	}

	//创建套接字  
	SOCKET slisten = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (slisten == INVALID_SOCKET)
	{
		printf("socket error !");
		return 0;
	}

	//绑定IP和端口  
	sockaddr_in sin;
	sin.sin_family = AF_INET;
	sin.sin_port = htons(8888);
	sin.sin_addr.S_un.S_addr = INADDR_ANY;

	if (bind(slisten, (LPSOCKADDR)&sin, sizeof(sin)) == SOCKET_ERROR)
	{
		printf("bind error !");
	}

	//开始监听  
	if (listen(slisten, 5) == SOCKET_ERROR)
	{
		printf("listen error !");
		return 0;
	}

	//循环接收数据  
	SOCKET sClient;
	sockaddr_in remoteAddr;
	int nAddrlen = sizeof(remoteAddr);
	
	//revData = (char*)malloc(sizeof(char) * 1000000);
	int i = 1;
	while (true)
	{
		printf("等待连接...\n");
		sClient = accept(slisten, (SOCKADDR *)&remoteAddr, &nAddrlen);
		if (sClient == INVALID_SOCKET)
		{
			printf("accept error !");
			continue;
		}
		printf("接受到一个连接：%s \r\n", inet_ntoa(remoteAddr.sin_addr));

		//接收数据  
		int ret = recv(sClient, revData, 3888888, 0);
		if (ret > 0)
		{
			revData[ret] = 0x00;
			json o = json::parse(revData);
			for (json::iterator it = o.begin(); it != o.end(); ++it) {
				//std::cout << it.key() << " : " << it.value() << "\n";
				if (it.key() == "imgA"|| it.key() == "imgB")
				{
					std::string num = std::to_string(i++);
					std::string strFileName = "D:\\"+ num +".jpg";
					std::string val = it.value();
					WritePhotoFile(strFileName, val);
				}
			
			}
			//std::cout<< json::parse(revData)<< std::endl;
			//printf(revData);
		}

		//发送数据  
		//const char * sendData = "你好，TCP客户端！\n";
		//send(sClient, sendData, strlen(sendData), 0);
		closesocket(sClient);
	}

	
	closesocket(slisten);
	WSACleanup();

	return 0;
}

2.Base64.cpp

#include"Base64_1.h"

CBase64::CBase64()
{

}

CBase64::~CBase64()
{

}

std::string CBase64::Encode(const char* Data, int DataByte)
{
	//编码表  
	const char EncodeTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	//返回值  
	std::string strEncode;
	unsigned char Tmp[4] = { 0 };
	int LineLength = 0;
	for (int i = 0; i<(int)(DataByte / 3); i++)
	{
		Tmp[1] = *Data++;
		Tmp[2] = *Data++;
		Tmp[3] = *Data++;
		strEncode += EncodeTable[Tmp[1] >> 2];
		strEncode += EncodeTable[((Tmp[1] << 4) | (Tmp[2] >> 4)) & 0x3F];
		strEncode += EncodeTable[((Tmp[2] << 2) | (Tmp[3] >> 6)) & 0x3F];
		strEncode += EncodeTable[Tmp[3] & 0x3F];
		if (LineLength += 4, LineLength == 76) { strEncode += "\r\n"; LineLength = 0; }
	}
	//对剩余数据进行编码  
	int Mod = DataByte % 3;
	if (Mod == 1)
	{
		Tmp[1] = *Data++;
		strEncode += EncodeTable[(Tmp[1] & 0xFC) >> 2];
		strEncode += EncodeTable[((Tmp[1] & 0x03) << 4)];
		strEncode += "==";
	}
	else if (Mod == 2)
	{
		Tmp[1] = *Data++;
		Tmp[2] = *Data++;
		strEncode += EncodeTable[(Tmp[1] & 0xFC) >> 2];
		strEncode += EncodeTable[((Tmp[1] & 0x03) << 4) | ((Tmp[2] & 0xF0) >> 4)];
		strEncode += EncodeTable[((Tmp[2] & 0x0F) << 2)];
		strEncode += "=";
	}

	return strEncode;
}

std::string CBase64::Decode(const char* Data, int DataByte, int& OutByte)
{
	//解码表  
	const char DecodeTable[] =
	{
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		62, // '+'  
		0, 0, 0,
		63, // '/'  
		52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // '0'-'9'  
		0, 0, 0, 0, 0, 0, 0,
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
		13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // 'A'-'Z'  
		0, 0, 0, 0, 0, 0,
		26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
		39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // 'a'-'z'  
	};
	//返回值  
	std::string strDecode;
	int nValue;
	int i = 0;
	while (i < DataByte)
	{
		if (*Data != '\r' && *Data != '\n')
		{
			nValue = DecodeTable[*Data++] << 18;
			nValue += DecodeTable[*Data++] << 12;
			strDecode += (nValue & 0x00FF0000) >> 16;
			OutByte++;
			if (*Data != '=')
			{
				nValue += DecodeTable[*Data++] << 6;
				strDecode += (nValue & 0x0000FF00) >> 8;
				OutByte++;
				if (*Data != '=')
				{
					nValue += DecodeTable[*Data++];
					strDecode += nValue & 0x000000FF;
					OutByte++;
				}
			}
			i += 4;
		}
		else// 回车换行,跳过  
		{
			Data++;
			i++;
		}
	}
	return strDecode;
}

3.Base64_1.h

//++Base64.h

#pragma once
#include <string>


class CBase64
{
public:
public:
	CBase64();
	~CBase64();

	/*编码
	DataByte
	[in]输入的数据长度,以字节为单位
	*/
	std::string Encode(const char* Data, int DataByte);

	/*解码
	DataByte
	[in]输入的数据长度,以字节为单位
	OutByte
	[out]输出的数据长度,以字节为单位,请不要通过返回值计算
	输出数据的长度
	*/
	std::string Decode(const char* Data, int DataByte, int& OutByte);

};

4.json.hpp 去网上下载吧，个人感觉比jsoncpp好用一些（我里面的json1.hpp就是json.hpp）

https://github.com/nlohmann/json/tree/develop/include/nlohmann

二.客户端

1.main.cpp

#include<WINSOCK2.H>
#include<STDIO.H>
#include<iostream>
#include<cstring>
#include <string>
#include <fstream>
#include "Bash64.h"
#include "json1.hpp"

using namespace std;
using json = nlohmann::json;
#pragma comment(lib, "ws2_32.lib")

char chBuf1[3888888], chBuf2[3888888];

int main()
{
	
	FILE *fIn1, *fIn2;
	int nRead1, nRead2;
	
	WORD sockVersion = MAKEWORD(2, 2);
	WSADATA data;
	if (WSAStartup(sockVersion, &data) != 0)
	{
		return 0;
	}

	std::string num = std::to_string(1);
	std::string chFileIn1 = "E:\\"+num+".jpg";
	num = std::to_string(2);
	std::string chFileIn2 = "E:\\" + num + ".jpg";

	SOCKET sclient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (sclient == INVALID_SOCKET)
	{
		printf("invalid socket!");
		return 0;
	}

	sockaddr_in serAddr;
	serAddr.sin_family = AF_INET;
	serAddr.sin_port = htons(8888);
	serAddr.sin_addr.S_un.S_addr = inet_addr("192.168.3.72");
	if (connect(sclient, (sockaddr *)&serAddr, sizeof(serAddr)) == SOCKET_ERROR)
	{  //连接失败 
		printf("connect error !");
		closesocket(sclient);
		return 0;
	}

	char chFileIn3[100], chFileIn4[100];
	strcpy(chFileIn3, chFileIn1.c_str());
	strcpy(chFileIn4, chFileIn2.c_str());
	fIn1 = fopen(chFileIn3, "rb");
	fIn2 = fopen(chFileIn4, "rb");
	if (fIn1 == NULL || fIn2 == NULL)
	{
		printf("打开读取文件失败");
		return 0;
	}
	//读文件
	json data1;

	//fread()读取成功返回值为实际读回的数据个数(单位为Byte)
	nRead1 = fread(chBuf1, sizeof(char), 3888888, fIn1);
	nRead2 = fread(chBuf2, sizeof(char), 3888888, fIn2);
	//base64编码 封装进json
	string imgBase64_1 = base64_encode(chBuf1, nRead1);
	string imgBase64_2 = base64_encode(chBuf2, nRead2);
	data1["imgA"] = imgBase64_1;
	data1["imgB"] = imgBase64_2;
	fclose(fIn1);
	fclose(fIn2);

	//显式转换为string 
	std::string s = data1.dump();
	const char * sendData;
	sendData = s.c_str();   //string转const char* 
							//char * sendData = "你好，TCP服务端，我是客户端\n";
	send(sclient, sendData, strlen(sendData), 0);

	//send()用来将数据由指定的socket传给对方主机
	//int send(int s, const void * msg, int len, unsigned int flags)
	//s为已建立好连接的socket，msg指向数据内容，len则为数据长度，参数flags一般设0
	//成功则返回实际传送出去的字符数，失败返回-1，错误原因存于error 

	char recData[266680];
	int ret = recv(sclient, recData, 266680, 0);
	if (ret>0) {
		recData[ret] = 0x00;
		//printf(recData);
	}
	closesocket(sclient);

	WSACleanup();
	system("pause");
	return 0;

}

2.Bash64.h

#ifndef __BASE64_H__
#define __BASE64_H__

#include <iostream>
#include <string>

static const std::string base64_chars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";

static inline bool is_base64(const char c)
{
	return (isalnum(c) || (c == '+') || (c == '/'));
}

std::string base64_encode(const char * bytes_to_encode, unsigned int in_len)
{
	std::string ret;
	int i = 0;
	int j = 0;
	unsigned char char_array_3[3];
	unsigned char char_array_4[4];

	while (in_len--)
	{
		char_array_3[i++] = *(bytes_to_encode++);
		if (i == 3)
		{
			char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
			char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
			char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
			char_array_4[3] = char_array_3[2] & 0x3f;
			for (i = 0; (i <4); i++)
			{
				ret += base64_chars[char_array_4[i]];
			}
			i = 0;
		}
	}
	if (i)
	{
		for (j = i; j < 3; j++)
		{
			char_array_3[j] = '\0';
		}

		char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
		char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
		char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
		char_array_4[3] = char_array_3[2] & 0x3f;

		for (j = 0; (j < i + 1); j++)
		{
			ret += base64_chars[char_array_4[j]];
		}

		while ((i++ < 3))
		{
			ret += '=';
		}

	}
	return ret;
}

std::string base64_decode(std::string const & encoded_string)
{
	int in_len = (int)encoded_string.size();
	int i = 0;
	int j = 0;
	int in_ = 0;
	unsigned char char_array_4[4], char_array_3[3];
	std::string ret;

	while (in_len-- && (encoded_string[in_] != '=') && is_base64(encoded_string[in_])) {
		char_array_4[i++] = encoded_string[in_]; in_++;
		if (i == 4) {
			for (i = 0; i <4; i++)
				char_array_4[i] = base64_chars.find(char_array_4[i]);

			char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
			char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
			char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

			for (i = 0; (i < 3); i++)
				ret += char_array_3[i];
			i = 0;
		}
	}
	if (i) {
		for (j = i; j <4; j++)
			char_array_4[j] = 0;

		for (j = 0; j <4; j++)
			char_array_4[j] = base64_chars.find(char_array_4[j]);

		char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
		char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
		char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];

		for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
	}

	return ret;
}
#endif

3.json.hpp 上面有链接（我里面的json1.hpp就是json.hpp）

Hit:服务端和客户端的Base64文件不一样，是因为当时服务端接收json时，Base64解码成图片出现了问题，又去找大神的博客，把服务端的Base64文件换了。然后能进行正常的传输图片，客户端就懒得换了~

C++ 实现json形式的Socket传输图片

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