<C/C++>Socket编程Http下载的简单实现(源码)

#include "HttpDownload.h" #define BUFFER_SIZE 1024 HttpDownload::HttpDownload(const char* hostAddr, const int port, const char* getPath, const char* saveFileName) { m_hostAddr = hostAddr; m_port = port; m_getPath = getPath; m_saveFileName = saveFileName; m_sock = 0; m_fp = NULL; m_fileTotalSize = 1; //没给0,因为分母 m_receivedDataSize = 0; m_cancelFlag = false; } HttpDownload::~HttpDownload() { } bool HttpDownload::initSocket() { m_sock = socket(AF_INET, SOCK_STREAM, 0); if (m_sock < 0) return false; //设置Socket为非阻塞模式 unsigned long mode = 1; if (ioctlsocket(m_sock, FIONBIO, &mode) < 0) return false; if (m_hostAddr.empty()) return false; struct sockaddr_in destaddr; destaddr.sin_family = AF_INET; destaddr.sin_port = htons(m_port); destaddr.sin_addr.s_addr = inet_addr(m_hostAddr.c_str()); int nRet = connect(m_sock, (struct sockaddr*)&destaddr, sizeof(destaddr)); if (nRet == 0) //如果立即连接成功 return true; //虽直接返回,但未立即成功,用select等待看socket是否可写来判断connect是否成功 if (WSAGetLastError() != WSAEWOULDBLOCK) return false; int retryCount = 0; while(1) { fd_set writeSet, exceptSet; FD_ZERO(&writeSet); FD_SET(m_sock, &writeSet); exceptSet = writeSet; struct timeval timeout; timeout.tv_sec = 3; timeout.tv_usec = 0; int err = select((int)m_sock+1, NULL, &writeSet, &exceptSet, &timeout); if (err < 0) //出错 break; if (err == 0) //超时 { if (++retryCount > 10) //重试10次 return false; continue; } if (FD_ISSET(m_sock, &writeSet)) return true; if (FD_ISSET(m_sock, &exceptSet)) break; } return false; } bool HttpDownload::sendRequest() { if (m_getPath.empty()) return false; char requestHeader[256]; //格式化请求头 int len = sprintf(requestHeader, "GET %s HTTP/1.1\r\n" "Host: %s\r\n" "Range: bytes=%I64d-\r\n" //从m_receivedDataSize位置开始 "Connection: close\r\n" "\r\n", m_getPath.c_str(), m_hostAddr.c_str(), m_receivedDataSize); int nSendBytes = 0; //已发送字节数 while(1) { fd_set writeSet; FD_ZERO(&writeSet); FD_SET(m_sock, &writeSet); struct timeval timeout; timeout.tv_sec = 3; timeout.tv_usec = 0; int err = select((int)m_sock+1, NULL, &writeSet, NULL, &timeout); if (err < 0) break; if (err == 0) continue; int nBytes = send(m_sock, requestHeader+nSendBytes, len, 0); if (nBytes < 0) { if (WSAGetLastError() != WSAEWOULDBLOCK) break; nBytes = 0; } nSendBytes += nBytes; //若一次未发完,累计,循环send len -= nBytes; if (len == 0) return true; } return false; } bool HttpDownload::receiveData() { char responseHeader[BUFFER_SIZE] = {0}; struct timeval timeout; timeout.tv_sec = 3; timeout.tv_usec = 0; //接收响应头 int retryCount = 0; int nRecvBytes = 0; //已接收字节数 while (1) { fd_set readSet; FD_ZERO(&readSet); FD_SET(m_sock, &readSet); int nRet = select(m_sock+1, &readSet, NULL, NULL, &timeout); if (nRet < 0) //出错 return false; if (nRet == 0) //超时 { if (++retryCount > 10) return false; continue; } retryCount = 0; if (recv(m_sock, responseHeader+nRecvBytes, 1, 0) <= 0) return false; nRecvBytes++; if (nRecvBytes >= BUFFER_SIZE) return false; if (nRecvBytes >= 4 && responseHeader[nRecvBytes-4]=='\r' && responseHeader[nRecvBytes-3]=='\n' && responseHeader[nRecvBytes-2]=='\r' && responseHeader[nRecvBytes-1]=='\n') break; } responseHeader[nRecvBytes] = '\0'; if (strncmp(responseHeader, "HTTP/", 5)) return false; int status = 0; float version = 0.0; ULONGLONG startPos, endPos, totalLength; startPos = endPos = totalLength = 0; if (sscanf(responseHeader, "HTTP/%f %d ", &version, &status) != 2) return false; char* findStr = strstr(responseHeader, "Content-Range: bytes "); if (findStr == NULL) return false; if (sscanf(findStr, "Content-Range: bytes %I64d-%I64d/%I64d", &startPos, &endPos, &totalLength) != 3) return false; if (status != 200 && status != 206 || totalLength == 0) return false; if (m_fileTotalSize == 1) //第一次获取HTTP响应头,保存目标文件总大小 m_fileTotalSize = totalLength; if (m_receivedDataSize != startPos) return false; //接收目标文件数据 retryCount = 0; while (1) { char buf[BUFFER_SIZE] = {0}; fd_set readSet; FD_ZERO(&readSet); FD_SET(m_sock, &readSet); int nRet = select((int)m_sock+1, &readSet, NULL, NULL, &timeout); if (nRet < 0) break; if (nRet == 0) { if (++retryCount > 10) break; continue; } int length = recv(m_sock, buf, BUFFER_SIZE, 0); if(length < 0) //出错 return false; if (length == 0) //socket被优雅关闭 return true; size_t written = fwrite(buf, sizeof(char), length, m_fp); if(written < length) return false; m_receivedDataSize += length; if (m_receivedDataSize == m_fileTotalSize) //文件接收完毕 { return true; } } return false; } bool HttpDownload::closeTransfer() { if (m_sock > 0) { if (closesocket(m_sock) < 0) return false; m_sock = 0; } else m_sock = 0; return true; } bool HttpDownload::start() { m_fp = fopen(m_saveFileName.c_str(), "wb"); //创建文件 if (m_fp == NULL) return false; bool errFlag = false; while(1) { if (!initSocket() || !sendRequest() || !receiveData()) { if (m_cancelFlag) { errFlag = true; break; } if (!closeTransfer()) { errFlag = true; break; } Sleep(1000); continue; } break; } if(m_fp != NULL) { fclose(m_fp); m_fp = NULL; } if (errFlag) return false; return true; } void HttpDownload::cancel() { m_cancelFlag = true; closeTransfer(); } void HttpDownload::getPos(ULONGLONG& totalSize, ULONGLONG& downloadSize) { totalSize = m_fileTotalSize; downloadSize = m_receivedDataSize; }