简单的C做一个HTTP POST并消耗响应的例子

我想创build一个非常简单的C应用程序来做一个HTTP POST。 这将需要几个参数，并使用这些来构build一个URL。 我只想做一个简单的HTTP POST，并得到没有使用curl的响应（这些库不会，也不会安装在需要运行的机器上）。

伪代码：

1. 过程2参数

2. 将参数放入模板URL： http : //api.somesite.com/apikey=ARG1&command=ARG2

3. 在生成的URL上执行POST

4. 消费回应

我的Google和SOsearch在这个问题上还没有放弃任何东西。

Answer 1

对不起，我花了这么长时间 – 这个周末我离开了。

消息具有由空行分隔的标题部分和消息体。 即使没有消息正文，总是需要空行。 头文件以一个命令开始，并且具有由冒号和空格分隔的键值对的附加行。 如果有消息体，它可以是任何你想要的东西。

标题中的行和标题末尾的空行必须以carraige return和linefeed对结尾（请参阅HTTP标题行分隔样式 ），这就是为什么这些行最后有\ r \ n。

URL的格式为http://host:port/path?query_string

向网站提交请求有两种主要方式：

• GET：查询string是可选的，但如果指定，则必须相当短。 由于这个标题可能只是GET命令，没有别的。 示例消息可以是：

   GET /path?query_string HTTP/1.0\r\n \r\n 

• POST：通常在查询string中的内容是在消息的正文中。 因此，标题需要包含Content-Type：和Content-Length：属性以及POST命令。 示例消息可以是：

   POST /path HTTP/1.0\r\n Content-Type: text/plain\r\n Content-Length: 12\r\n \r\n query_string 

因此，要回答您的问题：如果您对POSTing感兴趣的URL是http://api.somesite.com/apikey=ARG1&command=ARG2，那么没有正文或查询string，因此没有理由POST，因为那里是没有什么东西放在消息的内容，所以没有放在Content-Type：和Content-Length：;

如果你真的想，我想你可以发帖。 在这种情况下，您的消息将如下所示：

 POST /apikey=ARG1&command=ARG2 HTTP/1.0\r\n \r\n 

所以要发送消息的C程序需要：

• 创build一个套接字
• 查找IP地址
• 打开sockets
• 发送请求
• 等待回应
• closuressockets

发送和接收呼叫不一定会发送/接收所有给你的数据 – 它们将返回实际发送/接收的字节数。 您可以在循环中调用它们并发送/接收剩余的消息。

我在这个例子中没有做的是任何一种真正的错误检查 – 当某些事情失败时，我只是退出程序。 让我知道它是否适合你：

 #include <stdio.h> /* printf, sprintf */ #include <stdlib.h> /* exit */ #include <unistd.h> /* read, write, close */ #include <string.h> /* memcpy, memset */ #include <sys/socket.h> /* socket, connect */ #include <netinet/in.h> /* struct sockaddr_in, struct sockaddr */ #include <netdb.h> /* struct hostent, gethostbyname */ void error(const char *msg) { perror(msg); exit(0); } int main(int argc,char *argv[]) { /* first what are we going to send and where are we going to send it? */ int portno = 80; char *host = "api.somesite.com"; char *message_fmt = "POST /apikey=%s&command=%s HTTP/1.0\r\n\r\n"; struct hostent *server; struct sockaddr_in serv_addr; int sockfd, bytes, sent, received, total; char message[1024],response[4096]; if (argc < 3) { puts("Parameters: <apikey> <command>"); exit(0); } /* fill in the parameters */ sprintf(message,message_fmt,argv[1],argv[2]); printf("Request:\n%s\n",message); /* create the socket */ sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); /* lookup the ip address */ server = gethostbyname(host); if (server == NULL) error("ERROR, no such host"); /* fill in the structure */ memset(&serv_addr,0,sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); memcpy(&serv_addr.sin_addr.s_addr,server->h_addr,server->h_length); /* connect the socket */ if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); /* send the request */ total = strlen(message); sent = 0; do { bytes = write(sockfd,message+sent,total-sent); if (bytes < 0) error("ERROR writing message to socket"); if (bytes == 0) break; sent+=bytes; } while (sent < total); /* receive the response */ memset(response,0,sizeof(response)); total = sizeof(response)-1; received = 0; do { bytes = read(sockfd,response+received,total-received); if (bytes < 0) error("ERROR reading response from socket"); if (bytes == 0) break; received+=bytes; } while (received < total); if (received == total) error("ERROR storing complete response from socket"); /* close the socket */ close(sockfd); /* process response */ printf("Response:\n%s\n",response); return 0; } 

与其他答案一样，4096字节不是一个很大的回应。 我随机select了这个数字，假设对您的请求的回应会很短。 如果它可以是大的，你有两个select：

• 从响应中读取Content-Length：头，然后dynamic分配足够的内存来保存整个响应。
• 在文件到达时将响应写入文件

附加信息来回答评论中提出的问题：

如果您想在邮件正文中发布数据，该怎么办？ 那么你确实需要包含Content-Type：和Content-Length：标题。 Content-Length：是将标题与正文分开的空白行之后的所有内容的实际长度。

这是一个采用以下命令行参数的示例：

• 主办
• 港口
• 命令（GET或POST）
• path（不包括查询数据）
• 查询数据（放入GET的查询string并放入POST的主体）
• 标题列表（Content-Length：如果使用POST，则为自动）

所以，对于原来的问题你可以运行：

 a.out api.somesite.com 80 GET "/apikey=ARG1&command=ARG2" 

对于在评论中提出的问题，你可以运行：

 a.out api.somesite.com 80 POST / "name=ARG1&value=ARG2" "Content-Type: application/x-www-form-urlencoded" 

这里是代码：

 #include <stdio.h> /* printf, sprintf */ #include <stdlib.h> /* exit, atoi, malloc, free */ #include <unistd.h> /* read, write, close */ #include <string.h> /* memcpy, memset */ #include <sys/socket.h> /* socket, connect */ #include <netinet/in.h> /* struct sockaddr_in, struct sockaddr */ #include <netdb.h> /* struct hostent, gethostbyname */ void error(const char *msg) { perror(msg); exit(0); } int main(int argc,char *argv[]) { int i; /* first where are we going to send it? */ int portno = atoi(argv[2])>0?atoi(argv[2]):80; char *host = strlen(argv[1])>0?argv[1]:"localhost"; struct hostent *server; struct sockaddr_in serv_addr; int sockfd, bytes, sent, received, total, message_size; char *message, response[4096]; if (argc < 5) { puts("Parameters: <host> <port> <method> <path> [<data> [<headers>]]"); exit(0); } /* How big is the message? */ message_size=0; if(!strcmp(argv[3],"GET")) { message_size+=strlen("%s %s%s%s HTTP/1.0\r\n"); /* method */ message_size+=strlen(argv[3]); /* path */ message_size+=strlen(argv[4]); /* headers */ if(argc>5) message_size+=strlen(argv[5]); /* query string */ for(i=6;i<argc;i++) /* headers */ message_size+=strlen(argv[i])+strlen("\r\n"); message_size+=strlen("\r\n"); /* blank line */ } else { message_size+=strlen("%s %s HTTP/1.0\r\n"); message_size+=strlen(argv[3]); /* method */ message_size+=strlen(argv[4]); /* path */ for(i=6;i<argc;i++) /* headers */ message_size+=strlen(argv[i])+strlen("\r\n"); if(argc>5) message_size+=strlen("Content-Length: %d\r\n")+10; /* content length */ message_size+=strlen("\r\n"); /* blank line */ if(argc>5) message_size+=strlen(argv[5]); /* body */ } /* allocate space for the message */ message=malloc(message_size); /* fill in the parameters */ if(!strcmp(argv[3],"GET")) { if(argc>5) sprintf(message,"%s %s%s%s HTTP/1.0\r\n", strlen(argv[3])>0?argv[3]:"GET", /* method */ strlen(argv[4])>0?argv[4]:"/", /* path */ strlen(argv[5])>0?"?":"", /* ? */ strlen(argv[5])>0?argv[5]:""); /* query string */ else sprintf(message,"%s %s HTTP/1.0\r\n", strlen(argv[3])>0?argv[3]:"GET", /* method */ strlen(argv[4])>0?argv[4]:"/"); /* path */ for(i=6;i<argc;i++) /* headers */ {strcat(message,argv[i]);strcat(message,"\r\n");} strcat(message,"\r\n"); /* blank line */ } else { sprintf(message,"%s %s HTTP/1.0\r\n", strlen(argv[3])>0?argv[3]:"POST", /* method */ strlen(argv[4])>0?argv[4]:"/"); /* path */ for(i=6;i<argc;i++) /* headers */ {strcat(message,argv[i]);strcat(message,"\r\n");} if(argc>5) sprintf(message+strlen(message),"Content-Length: %d\r\n",strlen(argv[5])); strcat(message,"\r\n"); /* blank line */ if(argc>5) strcat(message,argv[5]); /* body */ } /* What are we going to send? */ printf("Request:\n%s\n",message); /* create the socket */ sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); /* lookup the ip address */ server = gethostbyname(host); if (server == NULL) error("ERROR, no such host"); /* fill in the structure */ memset(&serv_addr,0,sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); memcpy(&serv_addr.sin_addr.s_addr,server->h_addr,server->h_length); /* connect the socket */ if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); /* send the request */ total = strlen(message); sent = 0; do { bytes = write(sockfd,message+sent,total-sent); if (bytes < 0) error("ERROR writing message to socket"); if (bytes == 0) break; sent+=bytes; } while (sent < total); /* receive the response */ memset(response,0,sizeof(response)); total = sizeof(response)-1; received = 0; do { bytes = read(sockfd,response+received,total-received); if (bytes < 0) error("ERROR reading response from socket"); if (bytes == 0) break; received+=bytes; } while (received < total); if (received == total) error("ERROR storing complete response from socket"); /* close the socket */ close(sockfd); /* process response */ printf("Response:\n%s\n",response); free(message); return 0; } 

Answer 2

杰里的回答很好。 但是，它不处理大的回应。 处理这个简单的变化：

 memset(response, 0, sizeof(response)); total = sizeof(response)-1; received = 0; do { printf("RESPONSE: %s\n", response); // HANDLE RESPONSE CHUCK HERE BY, FOR EXAMPLE, SAVING TO A FILE. memset(response, 0, sizeof(response)); bytes = recv(sockfd, response, 1024, 0); if (bytes < 0) printf("ERROR reading response from socket"); if (bytes == 0) break; received+=bytes; } while (1); 

Answer 3

处理添加。
添加主机头。
增加了linux / windows支持，testing过（XP，WIN7）。
警告：错误：如果没有主机，path或端口作为参数，则为“段错误”。

 #include <stdio.h> /* printf, sprintf */ #include <stdlib.h> /* exit, atoi, malloc, free */ #include <unistd.h> /* read, write, close */ #include <string.h> /* memcpy, memset */ #ifdef __linux__ #include <sys/socket.h> /* socket, connect */ #include <netdb.h> /* struct hostent, gethostbyname */ #include <netinet/in.h> /* struct sockaddr_in, struct sockaddr */ #elif _WIN32 #include <winsock2.h> #include <ws2tcpip.h> #include <windows.h> #pragma comment(lib,"ws2_32.lib") //Winsock Library #else #endif void error(const char *msg) { perror(msg); exit(0); } int main(int argc,char *argv[]) { int i; struct hostent *server; struct sockaddr_in serv_addr; int bytes, sent, received, total, message_size; char *message, response[4096]; int portno = atoi(argv[2])>0?atoi(argv[2]):80; char *host = strlen(argv[1])>0?argv[1]:"localhost"; char *path = strlen(argv[4])>0?argv[4]:"/"; if (argc < 5) { puts("Parameters: <host> <port> <method> <path> [<data> [<headers>]]"); exit(0); } /* How big is the message? */ message_size=0; if(!strcmp(argv[3],"GET")) { printf("Process 1\n"); message_size+=strlen("%s %s%s%s HTTP/1.0\r\nHost: %s\r\n"); /* method */ message_size+=strlen(argv[3]); /* path */ message_size+=strlen(path); /* headers */ if(argc>5) message_size+=strlen(argv[5]); /* query string */ for(i=6;i<argc;i++) /* headers */ message_size+=strlen(argv[i])+strlen("\r\n"); message_size+=strlen("\r\n"); /* blank line */ } else { printf("Process 2\n"); message_size+=strlen("%s %s HTTP/1.0\r\nHost: %s\r\n"); message_size+=strlen(argv[3]); /* method */ message_size+=strlen(path); /* path */ for(i=6;i<argc;i++) /* headers */ message_size+=strlen(argv[i])+strlen("\r\n"); if(argc>5) message_size+=strlen("Content-Length: %d\r\n")+10; /* content length */ message_size+=strlen("\r\n"); /* blank line */ if(argc>5) message_size+=strlen(argv[5]); /* body */ } printf("Allocating...\n"); /* allocate space for the message */ message=malloc(message_size); /* fill in the parameters */ if(!strcmp(argv[3],"GET")) { if(argc>5) sprintf(message,"%s %s%s%s HTTP/1.0\r\nHost: %s\r\n", strlen(argv[3])>0?argv[3]:"GET", /* method */ path, /* path */ strlen(argv[5])>0?"?":"", /* ? */ strlen(argv[5])>0?argv[5]:"",host); /* query string */ else sprintf(message,"%s %s HTTP/1.0\r\nHost: %s\r\n", strlen(argv[3])>0?argv[3]:"GET", /* method */ path,host); /* path */ for(i=6;i<argc;i++) /* headers */ {strcat(message,argv[i]);strcat(message,"\r\n");} strcat(message,"\r\n"); /* blank line */ } else { sprintf(message,"%s %s HTTP/1.0\r\nHost: %s\r\n", strlen(argv[3])>0?argv[3]:"POST", /* method */ path,host); /* path */ for(i=6;i<argc;i++) /* headers */ {strcat(message,argv[i]);strcat(message,"\r\n");} if(argc>5) sprintf(message+strlen(message),"Content-Length: %d\r\n",(int)strlen(argv[5])); strcat(message,"\r\n"); /* blank line */ if(argc>5) strcat(message,argv[5]); /* body */ } printf("Processed\n"); /* What are we going to send? */ printf("Request:\n%s\n",message); /* lookup the ip address */ total = strlen(message); /* create the socket */ #ifdef _WIN32 WSADATA wsa; SOCKET s; printf("\nInitialising Winsock..."); if (WSAStartup(MAKEWORD(2,2),&wsa) != 0) { printf("Failed. Error Code : %d",WSAGetLastError()); return 1; } printf("Initialised.\n"); //Create a socket if((s = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET) { printf("Could not create socket : %d" , WSAGetLastError()); } printf("Socket created.\n"); server = gethostbyname(host); serv_addr.sin_addr.s_addr = inet_addr(server->h_addr); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); memset(&serv_addr,0,sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); memcpy(&serv_addr.sin_addr.s_addr,server->h_addr,server->h_length); //Connect to remote server if (connect(s , (struct sockaddr *)&serv_addr , sizeof(serv_addr)) < 0) { printf("connect failed with error code : %d" , WSAGetLastError()); return 1; } puts("Connected"); if( send(s , message , strlen(message) , 0) < 0) { printf("Send failed with error code : %d" , WSAGetLastError()); return 1; } puts("Data Send\n"); //Receive a reply from the server if((received = recv(s , response , 2000 , 0)) == SOCKET_ERROR) { printf("recv failed with error code : %d" , WSAGetLastError()); } puts("Reply received\n"); //Add a NULL terminating character to make it a proper string before printing response[received] = '\0'; puts(response); closesocket(s); WSACleanup(); #endif #ifdef __linux__ int sockfd; server = gethostbyname(host); if (server == NULL) error("ERROR, no such host"); sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); /* fill in the structure */ memset(&serv_addr,0,sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); memcpy(&serv_addr.sin_addr.s_addr,server->h_addr,server->h_length); /* connect the socket */ if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); /* send the request */ sent = 0; do { bytes = write(sockfd,message+sent,total-sent); if (bytes < 0) error("ERROR writing message to socket"); if (bytes == 0) break; sent+=bytes; } while (sent < total); /* receive the response */ memset(response, 0, sizeof(response)); total = sizeof(response)-1; received = 0; printf("Response: \n"); do { printf("%s", response); memset(response, 0, sizeof(response)); bytes = recv(sockfd, response, 1024, 0); if (bytes < 0) printf("ERROR reading response from socket"); if (bytes == 0) break; received+=bytes; } while (1); if (received == total) error("ERROR storing complete response from socket"); /* close the socket */ close(sockfd); #endif free(message); return 0; } 

Answer 4

经过数周的研究。 我想出了以下代码。 我相信这是将SSL与Web服务器进行安全连接所需的最低限度。

 #include <stdio.h> #include <openssl/ssl.h> #include <openssl/err.h> #include <openssl/bio.h> #define APIKEY "YOUR_API_KEY" #define HOST "YOUR_WEB_SERVER_URI" #define PORT "443" int main() { // // Initialize the variables // BIO* bio; SSL* ssl; SSL_CTX* ctx; // // Registers the SSL/TLS ciphers and digests. // // Basically start the security layer. // SSL_library_init(); // // Creates a new SSL_CTX object as a framework to establish TLS/SSL // or DTLS enabled connections // ctx = SSL_CTX_new(SSLv23_client_method()); // // -> Error check // if (ctx == NULL) { printf("Ctx is null\n"); } // // Creates a new BIO chain consisting of an SSL BIO // bio = BIO_new_ssl_connect(ctx); // // Use the variable from the beginning of the file to create a // string that contains the URL to the site that you want to connect // to while also specifying the port. // BIO_set_conn_hostname(bio, HOST ":" PORT); // // Attempts to connect the supplied BIO // if(BIO_do_connect(bio) <= 0) { printf("Failed connection\n"); return 1; } else { printf("Connected\n"); } // // The bare minimum to make a HTTP request. // char* write_buf = "POST / HTTP/1.1\r\n" "Host: " HOST "\r\n" "Authorization: Basic " APIKEY "\r\n" "Connection: close\r\n" "\r\n"; // // Attempts to write len bytes from buf to BIO // if(BIO_write(bio, write_buf, strlen(write_buf)) <= 0) { // // Handle failed writes here // if(!BIO_should_retry(bio)) { // Not worth implementing, but worth knowing. } // // -> Let us know about the failed writes // printf("Failed write\n"); } // // Variables used to read the response from the server // int size; char buf[1024]; // // Read the response message // for(;;) { // // Get chunks of the response 1023 at the time. // size = BIO_read(bio, buf, 1023); // // If no more data, then exit the loop // if(size <= 0) { break; } // // Terminate the string with a 0, to let know C when the string // ends. // buf[size] = 0; // // -> Print out the response // printf("%s", buf); } // // Clean after ourselves // BIO_free_all(bio); SSL_CTX_free(ctx); return 0; } 

上面的代码将详细解释如何与远程服务器build立TLS连接。

重要说明 ：此代码不检查公钥是否由有效的权威机构签名。 这意味着我不使用根证书进行validation。 不要忘记执行这个检查，否则你不会知道你是否连接正确的网站

当涉及到请求本身。 手工编写HTTP请求就没有什么了。

你也可以在这个链接下find如何在你的系统中安装openSSL的解释，以及如何编译代码，以便使用安全库 。

Answer 5

 #include<stdio.h> #include<stdlib.h> #include<string.h> int main() { FILE *in; char *p; char buff[512]; int id=6; int len; char str[100]= "curl -d 'uname=123&content=longitude' http://ipadress.com/path/to/"; if(!(in = popen(str, "r"))) { return 0; } while(fgets(buff, sizeof(buff), in)!=NULL) { printf("%s\n",buff); pclose(in); } }