Userland+LibC: Add a new little "tc" program for testing TCP.

Also added send() and recv() to LibC in support of this. They are just
wrappers around sendto() and recvfrom().

Userland/tc.cpp

@@ -0,0 +1,73 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+int main(int argc, char** argv)
+{
+    const char* addr_str = "127.0.0.1";
+    if (argc > 1)
+        addr_str = argv[1];
+
+    int fd = socket(AF_INET, SOCK_STREAM, 0);
+    if (fd < 0) {
+        perror("socket");
+        return 1;
+    } 
+
+    struct timeval timeout { 3, 0 };
+    int rc = setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
+    if (rc < 0) {
+        perror("setsockopt");
+        return 1;
+    }
+    rc = setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout));
+    if (rc < 0) {
+        perror("setsockopt");
+        return 1;
+    }
+
+    struct sockaddr_in dst_addr;
+    memset(&dst_addr, 0, sizeof(dst_addr));
+
+    dst_addr.sin_family = AF_INET;
+    dst_addr.sin_port = htons(8080);
+    rc = inet_pton(AF_INET, addr_str, &dst_addr.sin_addr);
+    if (rc < 0) {
+        perror("inet_pton");
+        return 1;
+    }
+
+    rc = connect(fd, (struct sockaddr*)&dst_addr, sizeof(dst_addr));
+    if (rc < 0) {
+        perror("connect");
+        return 1;
+    }
+
+    char buffer[BUFSIZ];
+    const char* msg = "Test message";
+
+    send(fd, (const char*)msg, strlen(msg), 0);
+    printf("Message sent.\n");
+
+    struct sockaddr_in src_addr;
+    socklen_t src_addr_len = sizeof(src_addr);
+    ssize_t nrecv = recv(fd, buffer, sizeof(buffer), 0);
+    if (nrecv < 0) {
+        perror("recvfrom");
+        return 1;
+    }
+    buffer[nrecv] = '\0';
+    printf("Server: %s\n", buffer);
+
+    rc = close(fd);
+    if (rc < 0) {
+        perror("close");
+        return 1;
+    }
+    return 0;
+}