socket tcp收发文件

socket服务端不断接收
接收端的缓冲区最好也设置为1024的整数倍，并根据文件大小适当的调整大小

#ifndef UNICODE
#define UNICODE
#endif

#define WIN32_LEAN_AND_MEAN

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <time.h>

// Need to link with Ws2_32.lib
#pragma comment(lib, "ws2_32.lib")
#pragma warning(disable:4996)


int main1(void)
{

    //----------------------
    // Initialize Winsock.
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        wprintf(L"WSAStartup failed with error: %ld\n", iResult);
        return 1;
    }
    //----------------------
    // Create a SOCKET for listening for
    // incoming connection requests.
    SOCKET ListenSocket;
    ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ListenSocket == INVALID_SOCKET) {
        wprintf(L"socket failed with error: %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }
    //----------------------
    // The sockaddr_in structure specifies the address family,
    // IP address, and port for the socket that is being bound.
    sockaddr_in service;
    service.sin_family = AF_INET;
    service.sin_addr.s_addr = INADDR_ANY;
    service.sin_port = htons(9999);

    if (bind(ListenSocket,
        (SOCKADDR*)&service, sizeof(service)) == SOCKET_ERROR) {
        wprintf(L"bind failed with error: %ld\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    //----------------------
    // Listen for incoming connection requests.
    // on the created socket
    if (listen(ListenSocket, 1) == SOCKET_ERROR) {
        wprintf(L"listen failed with error: %ld\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    //----------------------
    // Create a SOCKET for accepting incoming requests.
    SOCKET AcceptSocket;
    wprintf(L"Waiting for client to connect...\n");

    //----------------------
    // Accept the connection.
    AcceptSocket = accept(ListenSocket, NULL, NULL);
    if (AcceptSocket == INVALID_SOCKET) {
        wprintf(L"accept failed with error: %ld\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    else
        wprintf(L"Client connected.\n");

    //缓存大小,1024*80 以及 1024*320都不如1024*160的速度快（快1-2帧）
    const int BUFF_SIZE = 1024 * 160;
    char* recvbuf = new char[BUFF_SIZE];
    while (true) {
        clock_t t0 = clock();
        int iRecv = recv(AcceptSocket, recvbuf, BUFF_SIZE, 0);
        clock_t t1 = clock();
        printf("[%ld]%d ms recv a packet sized: %d \n", t1, (int)(t1 - t0), iRecv);
    }

    // No longer need server socket
    closesocket(ListenSocket);

    WSACleanup();
    return 0;
}
 

代码来源：微软文档 https://docs.microsoft.com/en-us/windows/win32/api/winsock/

---

socket使用tcp发送文件的注意事项：

1. 每次发送文件，都在加入数据头，标识文件大小等属性信息，用于接收时判断接收的大小。
2. 发送缓存区设置，比如我发送文件大小不到3m，缓存区从2m-6m，发现6m缓冲区的发送速度略高一点点。（一般人都是设置为1024整数倍，偏偏我按照文件大小设置缓存区，不是1024整数倍，造成接收每个数据头一包数据的速度很慢60ms+）

客户端服务发送文件，关键代码：

int socket_tcp_create(const char* ip, int port)
{
	int sockfd;
	int on = 1;

	struct sockaddr_in addr;
	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_port = htons(port);
	addr.sin_addr.s_addr = inet_addr(ip);
	
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if(sockfd < 0) {
		printf("Socket error\n");
		return -1;
	}

	if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (const char*)&on, sizeof(on)) < 0)
	{
		printf("setsockopt error: %s(errno: %d)\n",strerror(errno),errno);
        return -1;
	}
	// 4.设置发送缓存区大小
	unsigned int uiSendBuf = 1024 * 1024 * 6;
	printf("setsockopt of SO_SNDBUF = %d \n", uiSendBuf);
	int nResult = setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, (char*)&uiSendBuf, sizeof(uiSendBuf));
	if (nResult < 0)
	{
		printf("setsockopt of SO_SNDBUF failed - %d. \n", nResult);
	}

	if( connect(sockfd, (struct sockaddr*)&addr, sizeof(addr)) < 0){
        printf("connect error: %s(errno: %d)\n",strerror(errno),errno);
        return -1;
    }

	return sockfd;
}

int socket_sendto_tcp(int sockfd, char *buf, int len)
{
	 int iSend = send(sockfd, buf, len, 0);
	if (iSend < 0) {
		printf("send error\n");
		return -1;
	}
	else if(len != iSend) {
		printf("send msg to server len=%d, iSend=%d\n", len, iSend);
		return 0;
	}
}